Forsaken seem...really bad.

Are the Forsaken units really as bad as they seem? They really only seem to get good bonuses from Sorcerers, and even then they could just be replaced with Warriors. It seems the only time I use them is when I want to punish a unit of Marauders for being bad and turn them into Forsaken.

Am I not understanding the unit? Is there something I'm missing? If not, should I just write them off and not use them? Is there a mod to make them have a good place in the army?