Infernal mobs is a little unbalanced. On one hand it make the start incredibly hard if you get the wrong (or right) mob combo and have that mob stuck in your shelter. But becasue infernal mobs can come from spawners it make mob traps brokenly lucrative 30 mins on a single zombie spawner can potentially net you a full inv of enchanted gear sometimes books. It really makes the game easier if you make a spawn farmer, of course it isn't THAT easy as you have to land a killing blow to get the loot. Vengeance and ninja mobs tend to throw a spanner in the works but yeah with a little ingenuity you can get around that.
Luck can also make the start game super easy if you find a champ zombie trapped in a hole and it dropps a fortune/looting item.
I don't know what's in the UHS pack but this is compounded by any mechanism that allows auto monster farm makes Infernal mobs become EZ mode. Like iron spikes, LxP catalysts (not viable for one spawner) melee turtles so on and so forth.
That being said though I have not yet looked at the mods config if it has one you may be able to tweak dropps rendering the balance issues moot.
