You will find that the summoning dolls really have 2 uses:
1). To trigger traps
2). As mules to hold your loot
I would recommend that you do not put many points into your summoning dolls, they are just not worth wasting your points (actually I never put any points in summoning dolls anymore).
Also the 1st Summoning Doll is very useful. You will encounter several trapped areas in Act 1 where you can use the doll (parcours, the trapped hallways after you leave the room with the parcours, etc.).
