Your best off levellng a hybrid, so you can tank/heal and then damage when you wish. This worked wonders on my druid since i had a good tanking and healing set, i'd change spec twice a week but at least get to instance when i wanted. Your main problem as a rogue/mage like zealia said, is getting groups are a complete pain and i reckon getting into a decent guild will be way harder as a rogue or mage. Though if they're just starting kara your shiny epics wil make you a sexy option.
Just remember with 2.3 levelling from 1-60 is much faster.
Oh and, although i don't advocate it, if you check out a private wow "Fun" server, that should crush any urges to play wow for at least 5 months and you save yourself $30.
Man, just advising you has got me all fired up to play again!