Tried the Druid last evening. 'Dark Ages' map, otherwise normal settings. Not one ancient forest on the continent, but... Legendary Monsters summoned in mountains are nasty.
You'll either get Chimeras (large-area fire attack, Basilisks (large-area petrification attack), or Rocs (seem to be large melee nasties), haven't noticed them doing anything too funky.
Just don't get your druid killed, as I don't think you can hire any replacements (even apprentices), unlike a Necromancer. Then all your herbs will be useless.
Odditiy: Cannibals can be domesticated?