I had an interesting battle with an enemy who had cloned my armies (including shaman), the clone also used phatoms, creating more clones of the shaman.
I lost about a third of my troops in that battle (normally I lose none, archers+resurrect+phoenix meat shield).
Shaman have lots of hit points and a decent melee attack, it makes them pretty formidable for a level 4 unit.
In combat I normally use the Tactics powerup to have my Shaman a little bit forward, and on round 1 summon a phoenix infront of the shaman.
The phoenix will fly over, area attack 3 enemies (preferrably archers), and I'll put a death totem behind the phoenix.
Seems to work well, sometimes it damages the enemy, usually it just distracts a couple of enemy units, but once they've moved to the totem they tend to engage the phoenix (and stay away from my archers).
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roll a joint