They seem perfect for 4e
lurkers (any)
Controllers/artillery (red witches)
Skirmishers (diseased, gorgers)
Brutes (foamers)
I set them up as lvl 4ish creatures, but they were a big part of my previous world, Im hesitant to use them again. Im actually using more of the standard humanoids instead. (orcs, kobolds & hobgoblins were all replaced by ratmen clans in my 3.x world.)