I haven't seen a single Ent, so I wouldn't know.
Another good point that I'd like to add about the Shaman is that their special powers regenerate. So if you're lucky you can set up two or three totems of any one kind - or both. This is very helpful for boss fights when the boss summons lots of helpers, for example the Giant Spider in the Dwarven mines. With three healing Totems and three damage Totems all on the battlefield at once, not only were most of my units protected from attack, but I could almost completely ignore the summoned spiders and let my damage totems deal with them.
So for me the best unit I've gotten so far is the Orc Shaman.