How exactly is double weather an overpowered buff? If we're talking about healing, it's still the case that cure iv + double weather < cure v. Plus, we still have no reasonable alt heal while cure iv is in cooldown. Sch still could not pull main heal at all even with tier 2 weather.
Anyway ere's idea that I had:
Tier 1 and tier 2 can stack - giving a tier 3 weather.
Bonuses: Healing helix and normal helix have a reasonable punch at high level. IMO even tier 2 isn't a whole lot of a bonus when comparing high level heals and nukes.
Negative: Have EVERY element not of current tier 3 weather suffer penalty. Also, have weathers not manually removable, so you have to cast new weather in order to switch. This would make switching a little harder if you want to use it.