Each boss needs to feel like an MMO raid boss, which means large health pools and having players do enough damage. (gamasutra.com)
In fact, this soul system effectively gives you a team of characters with their own health pools and stats, as well as skills, which is pretty cool. (nerdybutflirty.com)
The main reason high health pools are «in» is because it's simply less time consuming for developers. (mmobro.com)