The problem is that ES is unlike the other two defenses because it adds, in effect, more HP. It was not designed to be this way, as I recall, but in the current game it’s basically just Blue Life. If they want to push it in this direction, then fine, let mages have pitiful life in exchange for high ES, but there need to be changes. Leech is a mess in general, but when you can leech with ES just as well as you can with Life, and ES is inherently higher than life, there’s an issue.
In my opinion, ES should largely be focused on recharge mechanics. I’ve seen it suggested that Ghost Reaver no longer convert leech to ES, but rather have Ghost Reaver allow your hits to instantly begin recharge when you would leech, boosting the recharge rate based on your leech %. I think it’s a good idea, at least.
As for evasion, I’ve never understood why we can’t have glancing blows. Like if a roll to hit succeeds, but is within a certain margin of your evasion, you take half damage because the hit only grazed you. Or, here’s another idea: How about evasion scales against damage? A single heavy blow is easy to evade, it’s slow and your character reacts faster. But large numbers of small hits are hard to evade. So evasion would be strong against one-shots, but fare worse against rapid hits.
As for armor, I don’t even know. In theory armor does what it should do: Straight reduction. The problem is the formula is awful and makes armor more-or-less mathematically incapable of dealing with damage past a certain point.
Honestly, I’d be happy if I could just stack defenses and have maybe 4k life and be fine. I feel like that’s the way it should be, but defenses are so weak that there’s no reason to invest in anything but life. Or ES, but again, ES is just Blue Life now.