I'll put it this way, if they inflate the lenght of the battle simply by expanding Mobs' HP pools, I'm going to be ticked.

If they make the fights more interesting by giving them beter behavior patterns and resistances, I should be ok with it.

But we honestly need a better party XP system than simply killing monsters out on the field, it's trite and boring no matter how long the individual fights are. And it teaches players nothing of endgame tactics they need to learn. I want real training runs for players.