Why would you buff Tibbers?
Annie
Molten Shield [E] - Now grants 10/20/30/40/50 resistances (Down from 20/30/40/50/60)
Summon Tibbers [R] - Casting Molten Shield will now grant it on Tibbers as well and give him a short decaying movement speed boost
The archaic design of this champ is already bad enough. You don't need to make Tibbers any better. If anything, you need to nerf the cooldown on R. It's so ridiculously short compared to other mages.
I remember there were one or two top lane champions who had their ult cooldown nerfed because it was right back up by the time you returned to lane. Annie is no different.