For characters that may survive the sleep spell. Summoning to the locked room, or behind centurions; and etc.

I'm not saying you must run without the zombies, but zombies are not always required, nor are mandatory to be fearful of you know the class well.

But I also agree the the fail rate is a bit too high and sometimes it made me to login less, when I had just 1-2 hours to play (because I'd have to log out as soon as I'd make a full army).

Probably I'd make a failure cooldown much less, or remove it at all, because killing a high level mob takes a while anyways. But guess this is a price for playing a powerhouse - play a long sessions or choose something else.