I'd like to see Quicksand nerfed to 2 pillars destroyed, Black Hole reduced to 2 per element, and SoG maybe 3 health regen.
Quicksand because it's too crippling against too many decks... you really need a pillarless deck to survive unless you get a good start and opponent gets a bad one.
Black Hole because it shuts down rainbow far too easily, whether pillar-based or supernova-based. 2 quanta per element would still be damaging, but that's a drop of 33%, which would give at least a slim fighting chance.
SoG because the quanta cost is low, healing is equal to a druidic staff, and you can get multiples out without needing to animate them. They fit in any deck, and everyone and their grandmother has at least a couple now that a lot of T50 farm decks have them.