I think such a change would take some getting used to, but I think it could be done in such a way so as not to be game breaking.
The point was brought up that conditions and CC would be too strong. So, make it so that the % based dodge only reduces direct damage but still completely avoids CC and condition application.
And I also feel like it should also scale off of healing power as well.
As for the actual scaling, I feel like it would work well if it started at a base of 50% reduction when you have zero bonus vitality, toughness, and healing power. And then from there, it should scale up very quickly at first with bonus t/v/h, but have diminishing returns such that you’d need infinity bonus t/v/h to achieve 100% reduction.
Maybe a scale that looked close to this:
(Tough + vit + heal) -> reduction %
0 -> 50% (no defensive stats on gear)
100 -> 60%
500 -> 75%
1000 -> 85%
1500 -> 90%
2000 -> 95%
2645 -> 98% (character in full ascended P/V/T with 30 points in 2/3 of the toughness, healing power, and vitality trait lines, omnomberry bread, dolyak runes, full defensive infusions)
Players with full P/V/T would take virtually no damage from dodged attacks while players in full glass would be taking half damage, and with something close to that scaling, it would highly incentivize throwing in at least a little bit of T/V/H as just getting up to a total of 500 bonus defensive stats will cut the damage you take from a dodged attack in half.
I also feel like if we moved to a system like this, the number of base dodges would need to go up by one, i.e. endurance cap changed to 150 so that anyone can hit 3 dodges in a row.
Also, any attacks that trigger something special when they successfully land (such as cloak and dagger) should still not trigger their effect when dodged. So, if you dodge a 5k CnD wearing zero defensive stats, you take 2.5k damage, but the thief does not stealth.
Overall, I think this is a rather creative idea that has a lot of potential. The primary drawback is that there may be further balancing issues I have no considered with certain PvE fights. Further, it may be a bit difficult for new players to get a grip on how it works, but I don’t think any more difficult than working out how a player’s armor total reduces damage.
Also, I think this change might unfairly buff direct damage in relation to condition damage. Perhaps dodged damaging conditions should still apply but at a reduced duration at the same % as the direct damage reduction. So, bleed, torment, burning, poison, and confusion still apply at a reduced duration when dodged, but weakness, chill, cripple, blindness, fear, and immobilize do not apply for any duration.
And the reduced duration should be applied to the modified duration, not the base. So, say a player dodges a bleed attack that has a base duration of 5 sec, the attacking player has +100% condition duration, and the dodging player has 1500 total bonus defensive stats, then the resulting applied bleed would be for only 1 sec.