How many level 60 classes to fully understand the game?

[SorenVC]

Hi. I was wondering if I ever bring my Iksar Necromancer to level 60 and maybe even do some successful raids, will I be able to get all the other 4 classes of Iksar to level 60 with little problems because pushing the Necro to level 60 taught me the entire game fundamentals?

Or do you think a real professional player needs at least 2 different or more classes at level 60?

I mean if I got a Necromancer to level 60 would I be able to get a Warrior or a Shadow Knight to level 60 with the same effort just taking longer because melee classes are harder to play?