I don't have too much of a problem with Shamir not being able to do much. Initially I thought it would be interesting if Shamir was basically useless because genies take on attributes of their masters, and Shamir's master is currently in a coma, so it would be like he had received a lobotomy. But obviously, that's not the way they wrote it.
But, honestly, I think you could argue that Shamir is only powerful where reality is concerned. He can change appearance and rain dazzle balls of fury down on you, but that doesn't mean that he can alter the fabric of reality. He can't necessarily change time or undo existence or transport you to another plane of existence. That's beyond his power because he deals in reality, not magic. He's a powerful being, but still lives in the same world everyone else does. The Black Cloaks are something altogether different and their powers are more arcane and unnatural. Still, it would be nice to have Shamir say something like that, because right now it does seem like he could be better utilized outside of a library. Like as a bodyguard or a gofer or something.