Okay, long post coming, because Hedge asked for it.
First off, I do agree that a lot of the Traits need rebalancing (possibly even most of them) but I’m not fond of OP’s ideas. Both changing existing things to completely different stuff, and built-in tradeoffs (i. e. you get bonus on this, but a penalty on that) are something I dislike. Most Traits already have the potential to be useful, but either compared to other stuff or even on their own they’re unbalanced; there also is already a native tradeoff in Trait choices in that you can only choose one per item. Of course, the current balance is such that in many cases there is only one useful option, so the tradeoff isn’t really there, but as the rest are balanced, it will become apparent.
I also still think that it might be a good idea to separate the Trait procs from crits, but that might be a too major change now. The variance in crit chance is huge: From the 5% base (afaik) to I think 45% momentarily, or up to 25% on some setups constantly. The crits by themselves are also already a powerful tool, and worth stacking on several Careers and weapons; the crit-based Traits only add to that. Balancing those Traits while taking the huge variance on Crit Chance into account is a huge chore, if not (nearly) impossible.
As for any particular Traits:
On Melee weapons, Swift Slaying seems to be the ruler now. It’s the primary reason crit builds appear to be the most popular stuff right now, and might be too strong on its own. In addition to its sheer strength (20% Attack Speed helps a lot at everything except single heavy hits), it also helps to keep itself up all the time, especially on already fast weapons. Putting a cooldown on its proccing could help, but that could easily make its use too inconstant and unreliable to feel good. Limiting its bonus would likely be a better direction.
Parry is the one Melee Trait I feel is where it’s supposed to be. It’s useful, but not on every weapon or setup; it gives a significant advantage, but that’s only momentary and still requires skill to use. The Dodge changes from the Big Balance Patch did (indirectly) reduce its effectiveness somewhat, but that might well have been warranted. If its parameters were to be tweaked, I think its activation window is the only thing possible, but it’d probably end up being either negligible, too strong or too weak.
Resourceful Combatant is near-useless now, even with high-crit setups. Limiting its procs to one every few seconds put a too big damper on it. As it is, the return on cooldown is negligible, and can be surpassed by the innate CDR effects with Swift Slaying, in addition to “wasting” several crits in the meantime. The reasons it used to be too strong was, again, the high proc rate some setups could reach (on Kerillian especially, with fast weapons and extra Crit Chance on them) and that it applied a static 2 second advancement to the skill cooldown (which made it way more effective on the already short cooldowns). I think its original design (or at least how it was meant to be) would’ve been the best: The reduction being a proportional part of the remaining cooldown, so that it’d be useful on every Career, somewhat more effective on the high-cooldown ones that actually need any reduction they can get. It would still make sense to limit the procs to one per strike, however, but not to several-second cooldown.
Off Balance’s biggest problem is probably that it doesn’t stack with other similar effects. It’s already limited in scope, mostly useful on Ironbreaker and certain other setups that block constantly (be it just for defense or as part of a push- or push-attack routine), so if there’s a WHC in the group, it goes near-useless, and having a bomber with Shrapnel reduces its effectiveness too. Getting these bonuses to stack would be strong, but I don’t think that situation would come up too often to be a significant issue, especially without a well-coordinated team. It would still leave Off Balance as a somewhat niche Trait, but one that could be used effectively.
Heroic Intervention is the one Trait I think could use a total rework, as I think it’s pretty much unsalvageable. Its effect is lifted pretty much directly from VT1, but the assist mechanic that made it moderately useful there got dropped out at some point during development of VT2. Unless someone feels like programming back the old assist mechanic (you get an “assist” whenever you kill an enemy that was about to hit your ally), it activates so rarely that it’s useless. And frankly, I think that getting in an extra mechanic for the sake of a single Trait is wasted work.
Opportunist seems too weak. So weak, in fact, that I’m not sure if it works as it should. Its effect should be strong enough to allow at least most weapons that normally cannot interrupt significant enemy attacks, to do just that. Those significant attacks are primarily any attack done by Elites; trash gets interrupted (and downright killed) easily enough, and their attacks are weak compared to Elites too. It also should have enough effect that it’s apparent that it works; as it is, it’s hard to track whether any attacks at all get interrupted with and without the Trait.
On the Ranged side, Resourceful Sharpshooter bumps into the same problems as its melee counterpart. Add in that ranged weapons aren’t generally used against hordes, and they have a consistent enough a tradeoff between penetration and firing speed, so the overly frequent procs aren’t even that problematic. Same thoughts about balancing as in melee side apply here too.
Heat Sink is the heat version of the former, and runs into similar troubles. In addition, its effect is way too limited now, even with Pyro’s heaps of Crit Chance, and doesn’t even work at all with the few weapons that could still effectively otherwise use it. In its former form, it also was the single worst offender (I think) about getting overly good with being bound to crit chance, with even Ironbreaker (who has no innate Crit Chance bonuses) using a Drakegun being capable of losing more heat than the big burst cost him. In all honesty, this might be another unfixable Trait without changing something fundamental. The best taht could probably be done would be to change its reward to a more limited form of the earlier (wit 1 heat lost per proc), and tying its proccing to headshots instead of crits (and probably, again, limited to one proc per attack or per a time unit), but even that probably would open it up for abuse.
Conservative Shooter is in a pretty good place, I think. In general, it allows only ammo sustain, but on certain weapons and situations (and with skill and a bit of luck involved), can be still used to gain a limited amount. A player with good aim can use it consistently to keep their ammo up, but it’s hard enough that not many even attempt it all the time. Its potential ammo gain could be limited (although I don’t think it needs to, as setting up multiple headshots on a single ammo isn’t easy) by limiting its procs to two or even one per shot, I guess.
Barrage and Hunter are both mostly good. I think their only problem is the effective selection of applicable weapons for each one, as any slow-firing weapon is effectively pretty much excluded on most Careers; they generally don’t get enough shots out either to utilize Barrage effectively, or to generate enough crits to use Hunter. There are effective builds to use both, though.
Inspirational Shot is a problematic one. In theory, it sounds kind of nice, and certain Careers can really use some additional Stamina regen. But in practice, getting enough headshots in to be effective with the Trait usually cannot be done in situations where the extra stamina is needed, and the whole team needs to have coordinated builds to get any real use out of it (as the selection of both weapons that can get enough headshots out to use the effect, and weapons that can take advantage of the extra stamina well are limited). Just for fun, I’ve also tried this out - and my friends had a hard time even saying if the build was effective. I really cannot figure out how this could made better, as its problems are quite fundamental, but I like the idea, so I have to reluctantly recommend a complete change or removal of the Trait.
Scrounger is good. Its interactions on certain weapons (Repeater Pistol) and attacks (Shotgun bash) could use some looking into, but otherwise, I have no complaints now.
With Thermal Equalizer my only complaint is that it’s a boring, passive bonus. It works fine, but doesn’t require any kind of activity to be effective; it just allows shooting more. Boring, but practical.
Necklaces are mostly good now, after the Big Balance. I haven’t used Barkskin significantly, but a friend has, and it’s been an effective enough backup, so it seems to have found its place for now. I’m not completely convinced it’s still worth picking up instead of the other Traits, but there you go.
Hand of Shallya is the only one I’m kind of worried about for now. It’s still only effective on (approximately) half the healing we find, and only if you heal someone else. Of course, the latter is mitigated by the Trait encouraging you to always use those Supplies on someone else, but that still leaves the problem of only half the healing items being applicable. All other Traits affect both items equally, and possibly other things too. Changing numbers alone isn’t likely to bring this in balance either, as I think if that “half the items only” is attempted to balance through effectiveness, it will end up being too strong on that half. I guess the best way would be to bring in an additional effect, applicable to Draughts, but I don’t know what it could be.
Charm Traits are pretty fine balance-wise (I guess Concoction is a bit too rarely useful, but even it has its place), but they have another problem: Grimoires. Grimoires replacing your potion means that at the end of most runs (at least on Legend) two people end up not being able to use their Charm Traits at all. This is compounded on some tough Careers, who end carrying the Grims nearly every time - and the first Grim is quite early in some maps (and in Skittergate, it’s both). So either a new Trait applicable to Grim carriers or a way to use Potions (likely immediately using a Potion you try to pick up) while carrying one would be hugely appreciated. The latter would also give more value to RV’s Master Brewer.
Trinkets have two issues, I think. The first one is simply the lack of options: There are only three Traits to choose from. This gets worse as Explosive Ordinance, useful as it might be, requires some retraining every time you change to or from it if you want to avoid friendly fire and still be effective. I also think that the AoE on grenades is already large enough for nearly all situations, especially as you can usually manipulate the enemies’ spread to some extent, so Ordinance loses on that account too. That leaves just two options to choose from.
For completely new Traits, I’d like to see something headshot-related in melee, but I don’t have any particular ideas.