The thing with shifters is that they are similar to changelings, taking up different forms and such, and the only way to find out their identity is to look at their eyes and magic. I feel that for someone who wouldn't know wht a shifter is and how to find one, I feel shifters are a bit of a Mary Sue/OP, etc. I would suggest that it would be a bit easier to make them more detectable. For example, with changelings, they would always have green eyes and magic, even if the one that they are imitating didn't have that, which can raise suspicion, making them less OP.

tl;dr Try and find other ways to make them less OP, but it's a great idea