I had big hopes for him, but when you see what Silva and Nasri are capable off you realise he will never be as good. Sure, they cost a lot to buy, but hopefully City can start scout talent and buy similar talents earlier for less money.
He's a risk defensively, yes. But IDK if I agree on his work rate. As you said, he doesn't track back as much as the rest. He seems to think he's some big shit, the Bendtner syndrome. He doesn't seem like he has anything to prove. So I don't know if I ever thought much about his work rate. I mean, it's easy to run when in possession if you don't participate in defending.
His biggest problem is that he's shit during 90 minutes performances, but an incredible impact player when he comes on late. When everyone else is tired. He's perfect to throw on due to his technique. When City want to attack, get a goal. But, you need balance over 90 minutes - defense and offense, passing, possession. He simply doesn't offer that. And City can't afford any passengers, specially not in CL.
It also doesn't help that he has quite the reputation of being a drinker and party attender.