PvE is too easy. Give chunks varying difficulty.

PvE is essentially a non-factor for every experienced player, but newer players just hopping in to the game, might get overwhelmed if mobs were just blanket-buffed. Solution? Make a difficulty setting that would buff mobs accordingly, and set their difficulty to higher. Mobs in structures such as strongholds should also be more difficult. Loot in higher difficulty areas should also have loot tables that yield better items.
Perhaps make some sort of indicator of how difficult a mob is, or how difficult the area you are in is. Possibly a new item? 
Probably make sure that the spawn chunk isn't too high difficulty, so that new players, again, don't get overwhelmed.