I played 4 games so far with summoning using Slann, Banner and 1 EoG. I think with this setup the summoning is balanced and fun against other good armies. Granted summoning does make my army a hell of a lot better then last edition but we needed something. The problems are with Kroak, Endless spells and multiple Engines. My fear is that with so many people abusing the system that they will knock us back down hard. I don't play Kroak so not sure how to fix him but for the others an easy fix would be make Engine of the Gods unique and make it so the Slann/Kroak cannot convert the bonus spells from endless spells or any other means into summoning points.