It's already relatively annoying to spot the difference between a monk and rogue (having to check the buffs ugh). Besides, it would only ruin certain weapons' uniqueness that are put on the back by default.
Yes! Do it now!
No! Rogues and Monks Will Just Look The Same
Rogues are all about quickness... if you're walking and you need to grab your blade quickly, do you think it'll take less time to grab the blade at your hip or to stick your hand up and grab the obvious blade on your back? Leave the back weapons to classes that have a reason to have it there... a 2-3 lb dagger doesn't go on your back... a 15-20 lb 2H will because you'd be tired of your pants falling down if you carried something heavy like that on your belt.
Give rogues tank spec! Then we can have weapons on back as a spec feature.
A witty saying proves nothing.
not quite Batman
Not everything. Just helms and back-sheathed weapons.