Amumu may have a 51% win rate but can he have mana reductions?

Ultimate - Mana 100/150/200 - Suggested Cost: 100/150/150 Bandage Toss - Mana costs - 80/90/100/110/120 - Suggested Cost: 80/90/100/100/100 Amumu has a weak early game so I want this to stay constant so that's why I kept his Mana costs high early but nerfed them slightly into later game.

These two have excellent mana costs. Despair RANGE: 300 COST: 8 MANA PER SECOND COOLDOWN: 1 Tantrum RANGE: 350 COST: 35 MANA COOLDOWN: 10 / 9 / 8 / 7 / 6

Sicne season 4 I've had an issue with this since I love maxing his Q first since I am so good with skillshots and also since it lowers the CD meaning I can cast it twice in one gank and deals tons of damage. But this really an issue since he has a tiny mana pool which is 287 – 967. At level 8 he has 518 mana which means for 1 teamfight if he Q's twice ,E's Twice Ults and uses W for 5 seconds he uses 240 + 105 + 40 + 100 = 485 Mana for 1 teamfight if you max Q first. And since I stopped building frozen heart since I find Randuins is better since I run 10% CD Scaling runes which gives me 40% at Max level with + + CD mastery . With randuins I get the slow which works wonders with Liandry's since it doubles the damage and I get health as well to help against magic damage.