Interesting for Storm? Not saying it's great, but I feel it deserves discussion. You can cast Ritual + Ritual and be able to ping off two creatures on the board and still continue your combo (or just go to your face or planeswalkers).
Cast Number | Total Damage (combined)
1 = 1
2 = 3
3 = 6
4 = 10
5 = 15
6 = 21
By instance or sorcery #6, you have lethal damage. May not need to cast as many spells. However, the obvious inherent weakness is it doesn't count moxen and other artifacts. That in itself makes it much weaker.