Cabal online is one Im currently playing also the level system so far isnt to grinding compared to the likes of silkroad online.
there are a few: (these all use the microtransaction system so no subscription they are all free):
corum online (graphics are outdated I have not tried this one yet)
cabal online (I play this one currently, its fun, nice sci fi graphics and not too grinding so far but im only level 19)
silkroad online (I played this for 200+ hours its addictive but so hard to find a server these days its always full, its very grinding though.....)
eudemons (I didnt like this the HUD is over crowded,quests are boring but also confusing when you first start)
navyfield (strategy online game, you pick a navy ship from 1 of 4 countrys buy weapons ,upgrades etc)
Airrivals (formally known as space cowboy, this game involves you flying around or using a land vehicle completing missions its not half bad and something different)