In my reasonably limited experience of online MTTs, the mini-raise utg with AA seems to be pretty common. The vast majority of people with AA utg seem to either flat call or mini-raise and then pray for the re-raise so I wouldn't discount it but most people seem to flat call or mini-raise low pps too.
However, if the table has been together a while and you are observant and feel that villain is too, then I think you can discount it based on that. He's only going to slow play AA utg or in ep if he's pretty damn sure he's getting re-raised. His nightmare in that scenario is that it gets called round and he's first to act in a family pot so if you feel that he feels that someone at the table is likely to reraise an utg mini-raise then you can't discount it. If, on the other hand, any ep raises are being folded round and you are pretty sure villain is aware of this, then i think you can more or less discount AA.