Since Demon synergy is pretty rare to see, and doesn't even work that well in PvE due to the only source of healing being Ella's Blood Ritual, I think a nice buff to Icepick would be to alter his Deal with the Devil ability. Currently, upgrading it makes it steal more health from an ally, potentially putting their life at risk. For starters, upgrading the ability should not increase damage dealt to the ally. Only the healing given to Icepick.
Secondly, it would be neat if, when on a team with Nitpick, Deal with the Devil takes stolen health and returns it to all Demon allies. Perhaps not 100% of it, maybe just 25% of the healing Icepick gets for each Demon ally, otherwise the healing would just be ridiculous!... but it would still help the Demon team be more viable in both PvP and PvE, I think.
Also Blood in the Water should enable all Demon allies to join in on attacking the target sorta like Reptile Pile on Viperia!!
Favorite hero: Hansuke
Currently: Waiting for new PvE content and the PvP revamp.