I guess they do look pretty similar, except Alice is more of a ginge and Oliver doesn't do facial hair :P I'm not really much of a Marvel fan (I have yet to see The Avengers, please don't kill me! :P) so I can't really speak for whatever similarities there may be between the two, but I guess it's just a fun dynamic to explore, which is probably why Marvel did it too :) (Plus, I've always been a sucker for the blonde + redhead aesthetic :P)
And maybe Kiara could use one of the other advisers? Like, maybe they couldn't find a specific faerie advisor so they just shoved all the faeries with somebody else??? *shruggety shrug* :/ I'm sure it'll get figured out in time :)