I would suggest Flyff but it's pretty much based on levels.
In Flyff it's hard to level, but in the private servers are easier to level sooooooooo, meh.
There are A LOOOOOOOOOOOOOOOOT of private servers.Flyff Private Servers
I use to play Eclipse flyff with my 2 sisters and my brother.
My brother was a Tank/Templar, female to be exact. Don't ask why, but they had good hp buffs and had A LOT OF HP.
My brother probably had like 2mil+ HP.
I was a Slayer, I also had a RingMaster or Seraph. RingMaster second class, Seraph 3rd. I don't remember which.
I also had an Arcanist, which is basically like an Elemental Class or w/e.
My sister was a max Seraph. Seraph basically is like a buff person.
Whenever my sister wasn't around I had to go on my RingMaster,Seraph to buff.
My other sister was, I forgot
All of our main classes were pretty much maxed.
Most servers have level caps over 100, and 200.
On the server I played the Level cap was 175. They probably raised it though sooooo, meeeeeeeeeeeeeeeeeeh.
We all had many classes and we had the OP mount * ^ *
Also, you can open more than one window ^ o ^
My brother had/has a very good PC and can open 3+ windows without lagging.
To be very 'pro' you have to spend a good amount of money x ^ x
Flyff is basically, overall, a very nice game with many, many classes and many, many skills.