It already takes 5 spells being used in the general vicinity and his ult already has a substantial mana cost if used multiple times in a short time period which you usually will do. Why not just give it the 5 spells charge as its cost or maybe reduce it altogether.
disregardable1 votesBecause his W is already free.
Catastrop1 votesWell that does help to make him more balanced, but seriously though, if he can't spam that W to regen mana he runs out of it quite easily especially in teamfight situations. So maybe a small reduction in the cost might be a bit beneficial for him overall.
disregardable1 votesI gotta tell you, I very rarely have mana trouble with him. He is supposed to build 
Catastrop1 votesHmm, then maybe I'm just too aggressive.