I don't get the putting Storm cards into historic. Surely it just massively impacts design space going forward, any number of spells could break them. I think Mind's Desire is the more dangerous, as you can conceivably do something degenerate off of a storm count of 4-5 which isn't particularly true with Tendrils.
The Storm cards actually kind of do make sense because they complement the Magecraft ability. Depending on what else they introduce to the format, it could be an exciting and cringe-worthy format to see.