There is a Power Cap? Like more talents wouldn’t have an effect anymore?
As for the difference in values. For most talents/traits/properties the general idea seems to be that you have
Unconditioned effects: Usually weaker but therefore permanently in effect (think Unbending Purpose or Properties)
Conditioned effects: Usually stronger but have some kind of trigger mechanic and sometimes timely limited (think Frenzied Flame, Castigate or even Skull-Splitter). For the conditioned effects one has to differentiate additionally between
Risk involved for trigger mechanic
Duration of buff effect
Active/Passive trigger
Availability of trigger
Especially, the conditioned effects are not as consistent as they should be with some trigger effects being so easy/riskless (think Castigate) despite providing highest boni. But overall the conditioned effects are stronger than the unconditioned. The same can be seen for weapon traits (conditioned) versus weapon properties (unconditioned).
I assume the different values are somewhat a sign of inconsistency which mainly stems from a more or less subjective feel of the designer of ‘how strong a certain talent for a certain career’ should be.
So the logic might be something along the lines: GK is a melee powerhouse, let’s give him 30%; Handmaiden is rather evasive, so give her just 15%. Additionally, there might be some reasoning involved that Adelion pointed out concerning the talent conditions.
I actually doubt that there is an overarching philosophy at play other than that a certain power threshold should not be exceeded for obvious reasons.
There’s sort of a power cap, but it’s not exactly at +40%
Every difficulty has a ‘max power’ setting, and for Legend that setting is 950 iirc. Which means that you can’t go over 950 power with power bonuses. You can math it out and find out that that comes at around 46% max bonus, in legend.
The cap in Cataclysm is 2k so there’s not really a worry about ever hitting that.
That aside, I agree with Kuli about the most likely reason for the inconsistency in power bonuses. It’s not about a specific breakpoint, it’s just someone going “Ok, so this buff is very easy to trigger and it’s on this class, and this class is supposed/not supposed to hit hard, so the buff should be…” and things like that.
OK SO, actually, it turns out that what I said about the power cap wasn’t so true.
So, MOST BUFFS (talents, properties, class buffs, etc) are actually applied after the calculations that check for the power cap.
The only exception to this is Volcanic Force, who does it beforehand, so most likely it’s just a mistake in Volcanic Force’s implementation rather than a real cap happening.
It’s been a while so I don’t quite remember all the details, but talking purely about the stagger row with the 7% power option: back in the WoM beta it used to be 15% and people ran the numbers and realised that made it flat out better than all the other options in that row in all or almost all cases, even vs staggered enemies. iirc it was calculated that at 7% there was an actual trade-off between using them, hence that talent gives 7% power since then.
At 10% the pure power talent would have still been stronger (I think that was before they made the stagger talents themselves easier to use/get to max stacks for ones that stack(ed) but don’t quote me on that).