Katu, i've read your aesthetics tutorial and it's pretty good...
Well, I have some suggestions to give...
Why don't you promote the "NIT" system (No Idle Time) Because most of the time, people quit because their enemies overpower them or the game is becoming boring..
I'll give an example-
Your character died and you have to wait for a minute for you to revive. You could put a mini game where people can play while waiting or something like that, or a game that depends less on level and items but more on skills.
Something like that....
Well, just a suggestion..
Cheers, meercat.