Not at all, Tobi being Obito will probably be explained and make a lot of sense. Also, him being a character we actually know something about (and who has had more than a single
line in the entire series) makes this more dramatic.
And don't give me the 'too obvious' bullshit. It's just an excuse to save face. Most people on the base thought he was Izuna (I base this on many, MANY polls), and a lot of people wanted him to be Kagami or even future Sasuke. Something that would neither make sense NOR have the desired impact.