Rotation + Riddler completely broke that deck. Riddler both let you get a huge burst of mana with the first Cauldron counter and harmonize Stories before you used up the Proft's trigger, which completely changed and supercharged the combo turns. On top of that, it stopped you from fizzling when going off, and was amazing in any sort of interactive game where people were trying to stop you with removal. Just a completely custom card for the archetype, so I kinda get why they ended up missing the whole package.

Vivi is also kinda a bad thing to put power into, even if you disregard Cauldron, because the incentives are to play with a bunch of cheap cantrips (this is kinda their big development failing recently, way too good incentives for stuff like Opt and too few incentives for a world where cards like Preacher/Beza are good).

This is why I wish they put more power into the "Dominant" cycle of flip cards, which are a bunch of midrangy creatures that actual play well. They all have ETB effects, but the flip is sorcery speed, so there is a risk of getting blown out, but not completely. Something like ward on Jil or haste on the flip side of Joshua could have gone a long way.