As long as you only get hit while at 100% toughness, it does not matter how much max toughness you have.
If you get hit by two melee attacks in a row, the first attack will be absorbed by your toughness, while the second one will deal damage to your hp, based on the % of your toughness missing after the first attack.
Investing into more max toughness will make you lose a smaller absolute amount of hit points, since a larger % of your toughness remains after taking the first hit.
However, investing into max HP instead, will make you lose a smaller relative amount of your max HP, which is more important.
Unless you only take single melee hits with a time interval in between, which allows you to get back to 100% toughness only if you increased your max toughness, getting more survivability out of increasing your max toughness rather than increasing your max HP, is quite difficult.
If you are getting shot by ranged units a lot, increasing your toughness can be useful, because you will not take any health damage from ranged attacks as long as toughness is up.
Taking a bunch of (ranged)hits can actually result in you losing a smaller % of your max hp, if you invested into toughness.
If increasing your max toughness would be useful for you, because you tend to take a lot of ranged damage, you should probably start with running gunner resistance perks on your curios, rather than investing into toughness at the cost of max HP.
However, you are not suggesting to run gunne resistance curio perks in the above mentioned section of your guide.
Yes it does. But if you have plenty of toughness regen, it does not really matter if you need to regen 70% or 40% of your toughness.
Some attacks effectively ignore your toughness, so additional max toughness provides no value there.
The same thing could be said about bursters.
But that one time when you canât see or hear it coming itâs going to hurt and a lot. Burster explosions are one of the few things that can simply end a run. Almost all of the other stuff you can see coming and learn to position better. At times there is just nothing you can do about a burster jumping out of a door, or from behind a bunch of bulwarks/crushers and that burster resistance perk makes all the difference when that happens.
I did not see your guide specifying that you are talking about auric maelstrom only.
I personally do not have any issues with snipers downing or killing me. I might get hit by a sniper once every 20 matches or so. To me, that is not worth taking a few sniper damage resistance perks. Apparently, the sniper issue is quite subjective.
Generally speaking, if a player frequently dies completely after running out of wounds, they should probably equip 1 wound curio (or step down a difficulty).
If you die sometimes, because a sniper hits you when you are sitting on 1/2 wounds, you can avoid that by taking 1 wound curio. You can drop your sniper resistance perks and run 3x 5% max HP or max toughness instead, which will almost entirely offset the HP or toughness lost from swapping to the +1 wound main stat.
If you want to reduce the damage you take from snipers, you might also want to switch from max toughness to max hp, since toughness is of no value, when a sniper shoots you.
Unless you run premades only, where you always have someone else taking care of bursters in a safe manner, this is not true.
If it is your opinion, that no psyker should ever try to push a burster, or stand anywhere near a teammate when a burster is closing in, then all poxburster hits could indeed be blamed on positioning errors.
If that is not what you are trying to tell me, i guess you have to agree that me taking damage due to
- a teammate shooting the burster that i am pushing
- a teammate failing to push a burster that is going for them
is not my fault.
Certainly not well enough to even be compared to one with Flurry & Rending as a meta choice. Imo. 
