If you can dodge well (only thing I’m decent at in RotMG. Kind of.) extra health is unnecessary and mana gives you either more damage to kill the thing attacking you quicker, or buff you, or heal up the missing health anyway.
Of course you’re more vulnerable to insta kills, but since I know what could kill me that quick I can make sure I don’t get destroyed. If there are moments where it’s very hard to not take damage (bullet hell fights like Oryx 2 new phases) or you’re suddenly unable to move (those damned MT archers) then health would be more useful, but you can 1. Know when those situations would come up (I’m talking about things like O2 or Daichi or Colossus) and swap rings, 2. Avoid most of those situations, and if you can’t, then you’re in trouble. Whatever.
I just like having more ability uses than more health. Maybe that’s why I die so much