The OP might look at other people that have no life and play game for 24/7 and envy them.
The DoH/DoL class take too much time to lv up ( without helping hand of cause! )
If people can play only 2-3 hour per day, it will take around 40-50 days to finish 1 DoH class
So it take around 9-10 month to reach all DoH classes ( assumed you play everyday! )

DoL is a time-consuming class too because you have to walk around to find node and that count as time sink too.
I bet it might take some 4-5 month to reach lv 50 of all DoL classes

DoW/DoM is kind of easy if you have PLer.
But finding dedicate PLer that will PL you every class to 50 is very hard ==' Who gonna help you for many many hours and he go nothing in return? ( If you are REAL girl it would be another story :P )
So lvl DoW/DoM class might take another 3-4 month at least for soloing and PTing sometime.

So total time is around 1 year+ to reach all 50 classes,
And this game also released for more than 1 year, no wonder why ppl reach all 50.
But for new player, it will take another 1 year to lv up everything. And I think that's the correct pace.
After 2.0 launch, SE might lift lv cap and everything should be good-to-go again