Resol Forest or those rank 2 areas? What is your go to area for EXP farming?
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I'm all about North Aelio personally, love killing the veteran enemies since they give me good practice on learning any new classes and how to play them. Vanford is my 2nd pick.
Once you unlock rank 2, head to those or yeah the forest(mobs are 15). Rank 1 is way too slow after level 15.
Exp is stunted if enemies are 5 lvls above or below you, so being in your lvl range is the most efficient way to lvl.
Lab you get your little floaty robot to buff and do some damage too.
I like to mix up all 3 though just for a change.
Using the "Room" option on the teleporter (and toggle first option to search area where you are and want) to find a group is the most important thing for good xp speed imo (or having friends).