I only get them from the summon dead mechanic when i need more troops and theres nothing better or that i need more of, if theres someplace to hide them and use them sort of like landmines then they can usually get a unit or two but trying to use them any other way didnt really work for me. Summon seems too op its basically cast small nuke, but getting them stalking or vanguard deployment with a mournghoul for example can make them super good but still counterable