The health of some trash mobs are high and it makes for not a difficult or challenging dungeon but a long drawn out one. In Darklight/AF2/Relic group, we can kill the bosses in AK faster than some of the packs leading up to it. I don't mind trash mobs but when they are needlessly damage sponges for the purpose of soaking up our time - it's just tedious.

A good example of this imbalance is 1 Dullahan dies rather quickly.
But from a pack - just 1 monster has the health of 2 Dullahan. Again, tedious and unneeded. This is probably the reason why so many people opted for speed runs in the first place.