Is HP really that great of an indicator anymore? Lots of the new gear seems very heavy on Endurance, regardless of class or spec, to the detriment of other stats.
I've inspected quite a few 55s with absolute garbage gear, mostly Basic / Black Market / Arkanian with heavy endurance and poor secondary stats.
Of course it isn't totally their fault, gear itemization at 55 right now is crap for almost every class. And for some, it actually gets worse the better the gear (more endurance and less main / sec stat going to an Ultimate piece over an Elite).
If you want to set minimums, I'd look for other stats to measure and actually inspect the players.