With 20 of them, that's 5 hold persons per PC. It's basically a TPK. Hold all the PCs. Cast Spike Growth. Cast Thorn Whip. Drag held PCs through spikes. Fun!
Yeah it does sound lethal! I think I'll dial the basic creature down to 1st level druid spellcasting ability and maybe give the sub-leader 3rd level. Does that sound reasonable for CR 1/2 vs 6th level PCs?
I'm also considering changing them from undead to plant. Nothing to say they couldn't have been created through a natural process. Would this require any major design changes?
Resurrecting this thread as adapting them myself - the original monsters predated cantrips as they were first edition. Makes more sense to give them the use of a cantrip each. Reserve druid spells for leaders (4HD in original WD21) and the jarls. @Helm how did it go in the end? Did you use them?