For me, maybe not for you idk, 800 or 700 hp can do a big difference if you are hit, for example, by a mortal strike (minotaurs, rends, etc...). From my perspective the max hp vs the max damage are 2 separate builds that force the player to make a choice. I can add more elements that can put into discussion an hypothetical "best build", like slayers, like non mounted fights and situations when you lack a decent single target atk to kill high hp mobs, like reducing phy resistance to improve RPD, If you look closely there is always something that interfere with the static idea of "best build".
To "solve the problem" of situational fights i like to key bind different types of sets, i remove the SoT if RPD is the way to go, i switch my regular weapon with a slayer and so on. Most of the times i do this for fun. Sometimes I need to switch the equipment to economize time, for example while i run the gauntlet where 5 of 6 bosses are affected by slayer weapons or while i fight an high level fungal marsh from giant/gynormous stash notes, very hard to hit, but easy to kill with RPD.
Just to clarify what i mean: try to compare this shard with wow PVE: in wow each char need to focus on one single role, a fixed build made with the best in slot paradigm make sense, if you are a DPS you don't need to waste skill points or gear stats on heals, because an healer will do the job for you. Here the player must face a lot of different situations alone, covering all the roles at the same time (dps/healer/tank). In the end for me the UOEX gameplay is heavily situational.