1. i read somewhere, the more HP you have, the more sexy you are
2. i'm not abandoning my defense stats for HP - currently having some 28+k hp, i just asked how is that possible
3. i have equipped 4 pieces of Battlemaster outfit (ofc with PvE mods in)- after leap i have 10% dmg increase for 5 seconds - better smash, better vicious slash => better agro on me, also every intercede (leap to friendly) nets me 2.3-2.4k HP - this is actually big help (and it is counted off the overall HP you have).
I actually intercede to teammates as much as i can (every 20 secs +2.4khp is nice) - i help my healer and i dump agro off my teammates, also if i intercede to healer (usually standing farther from battle) i immediately can/do jump back on target => free force scream, unstoppable, rage building ... big benefits.
4. as mentioned above, it's also insurance if something 'oh crap' happens, you survive and give your healer time to react
So you can see at least in my case it is big help for me having more HP and in my case it comes with the kind of play i do - lots of intercede...