Another two good ways for SE to solve this... are the following ones:

1- Give me some reward, or cookies, so I spread the word, telling how wonderful marauder/warriors can be to everyone so they open their eyes and start playing with them.
2- Assault player's houses and put them a gun aside the head "PLAY TANK".
3- Less radical, easier for everyone!... Select a 50% of the population of the server to be obligated to play healer or tanks during three days, so they can't use any other clases (Neither crafters, or they'd prefer to craft instead of tanking/healing). Then after three days, the other 50% does it, and so on, FORCE THEM AND BE HAPPy, yay!

PS: Please don't take me so seriously, I don't want some ragecomments because this, I'm just following the happy-funny joking line of the OP.