The devs did a stream to showcase his abilities, and he's actually incredibly very team dependent despite his "no healing/buffs from allies" rule.
all of his abilities are extremely slow, for example his Q is a channelled aoe firebreath which unlike diablo he can't rotate during the channel, meaning it's up to his team's crowd control to keep the enemy under the fire. They also have big windups and delays allowing every other solo laner (and high-mobility hero) in the game to move around him and outplay him massively. He also has one very short range dash as his only in-combat-escape mobility tool making him very unsafe from getting ganked when he's alone. He also has the largest hitbox in the game which further makes him very punishable for not having someone cover his weaknesses.
Pretty much the best way for him to actually consistently land those abilities, is he needs enemies to be inhibited by someone else.
He's also not that great as a solo pusher; he has to spend basically his entire energy bar to clear a single wave (which regenerates slower than normal energy bars) ,and his damage to structures is literally halved. The ideal way to play, is basically to focus on constant teamfight action.
Basically, you aren't going to be doing the murky/vikings thing where you avoid fights and do your own splitpushing while raking in that exp contribution, since that's the intended optimally designed method of contribution, you have to go fight and kill the enemy team (with your team). Which ideally means pairing up with good crowd control/tanks. So far, it seems the perfect teammate to fight with is thrall who's earthquake ult pairs excellently with deathwing's ult for a wombo combo.
