So, why does Ivern get free buffs for his team?
Ivern's winrate is very high, we all know that. It might be not because of his kit, but because of itemization. Yet there's one thing in his kit that imo makes no sense. Ivern doesn't have to give his buffs up, because he gets 4 for free (not counting enemy buffs).
Having a midlaner with blue buff, a toplaner/adc with red buff and Ivern with a double buff is a HUGE advantage. Basically, Ivern gets a free slow and sustain + no mana issues for 2 minutes, his toplaner/adc gets free damage and sustain, and his mid gets free cdr and mana regen; all this at the cost of nothing for Ivern.
Also, if he invades and manages to get enemy buffs, he can have 3 PEOPLE on his team with double buff. Honestly, it seems stupid to me.
If you want to nerf him, start with removing some stuff that makes no sense like this "free buffs" thing. After all his winrate is high not because he carries games through damage, but because he's extremely good at giving his team options to carry for him.