The Aran are not completed?

no,it really isnt valid.
no more claases,maybe a sub-job for aran one will be aran pole arm and one will be aran blunt weapon,this is the only thing that can happen but not likely it will.

The game isn't coded in a block of stone somewhere in the depths of nexon's vault... anything can happen.

The only evidence that there are not "more" Aran classes, or that Aran refers to just the spearman is limited to the fact nothing else has been released yet. There could be more still to come, only time will tell.