The current formula for stun avoidance is:
2x(damage received)/(maximum health+stun avoidance).
edit: that’s the formula listed in game. the wiki says the denominator also includes current ward, in which case the ward stackers are also fine.
The game seems to encourage a couple different ways of defending your character, either maxing out health or protections. Health is already far easier as it’s just one stat to focus on. Maximize your health, get your glancing blow capped and you’re in a pretty good spot.
Getting protections is harder, and you have to keep your health pool down. This makes you much more vulnerable to stun. From the endgame arenas I’ve watched people are running around with 2.5k health or so.
You would need t5 stun avoidance rolls on most of your equipment to get that kind of defense against stuns via stun avoidance which would leave very little room for getting the protections you need. And even if you got that much stun avoidance, the health maximizers got it passively just by boosting their primary defense.
I think the formula needs a bit of adjustment in favor of people actually putting points into stun avoidance, something more along the lines of:
2x(damage dealt)/((0.5xhealth)+3x(stun avoidance)).
No promises that those numbers work out, I’ll leave the exact math to someone with the actual numbers to work with. But in general, reduce the effectiveness of health and greatly increase that of stun avoidance for the purpose of avoiding stuns.