He's clearly extremely talented but the fact that he's so versatile and tactically aware will ruin his career. He was being talked up as the best young AM in the World, scored 5 Champions League goals in his first season and was the main man for Brazil under Menezes but since Mourinho came he's reached nowhere near that level.
I'm not sure Mourinho is the best manager to further his development as a footballer. Joining Arsenal would have been the better move. I'm struggling to think of a footballer that has progressed technically under him, mentally or tactically is a different matter altogether.
That's rubbish. Oscar is showing his best ever football this season for Chelsea. He's playing at a higher level than he's ever played. The fact you think he was better in his first season shows you don't know what you're talking about. Excluding a 3 month period under Di Matteo, Oscar wasn't that good under Benitez. Since you mention goals, believe it or not, his goals to games ratio last season under Mourinho was better than it was in his first season. It's under Mourinho that Oscar has been at his best. As for joining Arsenal, well Oscar is in football to win at the highest level not to join a clueless manager in a mediocre team. There's a reason why Arsenal fans want Wenger out. Drogba clearly improved technically under Mourinho. So did Lampard and a host of others.
As for being the main man under Menezes, well he was actually played in his normal position as a number 10. Scolari came in and took away his number 10 position, both literally (giving the 10 jersey to Neymar) and on the pitch. Oscar was shafted out to the right. Now under Dunga, he's again shafted out-wide, only this time, to the left.