So, for now, let's try total immunity to your own Dominion Sphere sla effects, and we'll see if that needs to be changed.
You can also still make things permanent, if you want, 3/whatever.
PS, I disagree that Dominion as written is terrible and no one ever takes it. It's one of my favorite spheres because like domains, you have to balance the power granted against the spells given, only spheres, spells are way more important, and outside of minion creating spheres, dominion and stone are the only ones that gives you large AoE battlefield control effects. Most Spheres feature only instant attack spells, or spells that might as well be instant (like Resilient Sphere, in that it's actual effect is usually similar to Maze, but you can use it for other things).