I only have 4 50s and I have to say the only reason I dont have all 50s is because I dont like leveling, I like endgame content and player created content. If it took a long time to level each class then I would still only have 1 50 which would mean I would be gimping many parties and endgame content.

OP if you want to level slow then do it, the mechanics are there for it dont try and force everyone into your play style.