So far you are the only one I can agree with fully 100%.Aqualad- ENFJ or INFJ. I'd say ENFJ because in the show he shows primarily uses Fe
Robin- XNTJ. He's to structured to be a P
Superboy- ISTP. It's a little hard to tell because he's so brooding all the time, but it seems like all his feelings stuff has to do with his situation. I could see an arguement for F though. He certainly goes into blind rage a lot for a T. My guess is an immature T.
Megan- ESFP. She doesn't seem quite wierd enough to be a textbook ESFP but she definity uses Fi not Fe.
Artimus- ESTJ. I'm not 100% sure on this one. She has that rebel thing going for her which is kind of rare in for someone with Si but she also tells it like it is, very representative of ESTJ's. If an SJ is going to be a rebel they are most likely an ESTJ with developed tertiary Ne. Could also be an ENTP, though she doesn't really strike me as one.
Wally- ESTP. No way he's a feeler. He's shows no Fi at all and is really into Ti science stuff. Seems pretty obvious in the episode with the tower and the magic.