Quote (Goomshill @ Mar 5 2022 06:12am)

In both PvM and PvP it has an effect, but its of dubious value. Its a form of damage mitigation that only works against a subset of attacks and not while running and has diminishing returns
Its better for characters who only attack or cast, not run, ie any char with enigma. Otherwise you need to walk to retain defense which slows you down significantly, and in general walking/running chars are trash anyway
In PvP there's only a handful of FFA matchups where defense matters, everything else is autohit. Sins and barbs who use whirlwind, mostly. There are some other chars who use attack rating checks that are less relevant, either a secondary attacks or with such astronomical attack rating you can't stack against it. Like against a pally it can make charge whiff, but won't stop smite. Against BvCs, defense is a big deal, its why bvc vs anti-barb smiter is a dumb matchup that involves angelics set and chant vs exile and ebugs, then you get doom and clegs and sync vs flash freeze telesmites
In PvM defense is way more relevant at mitigating damage but its also way less of a threat to begin with, you can pretty comfortably pvm on a 2k hp char with max resists and nothing else to mitigate, let alone some 20k defense 8k hp cock mongrel barbarian. At least defense is pretty relevant at helping keep your merc alive since he usually soaks up more direct attacks, and doesn't lose his defense while moving afaik. Still there's no shortage of monsters who ignore defense. Most spell projectiles and a few melee abilities, notably monster charge which is autohit. If you look at level 85 trash mobs in chaos for example, they've got 4.1k/6.1k/5.5k ar on their attacks, every spell from oblivion knights, venom lord inferno and finger mage spider missiles all ignore defense. So if you had a level 90 merc against a 5.2k ar level 85 enemy, he's got a chance to be hit of:
1000 defense = 81%
2000 defense = 70%
4000 defense = 55%
8000 defense = 38%
12000 defense = 29%
16000 defense = 24%