Even after the Brightwing nerfs he is still pretty legit. You just need to play a bit differently. Anymore what I do is basically blow my entire wad of mana doing my QWE rotation basically on cooldown, disengage the combat, hearthstone, Z back into the battle. It is an ungodly amount of healing. You can reasonably expect to be ahead in the teamfight after you blow your rotation so you leaving the battle to refill your mana isn't the worst thing in the world. If you take Rewind/Hardened Focus you can really blow your mana quickly. Then, of course, you're taking Rains at 7. I'm still pretty damn close to the healing numbers after the game pre-nerf when Blink procced Rains and Path of the Wizard meant unlimited mana. But I do use Hearthstone on him about 10x more than on any other hero.