It is. Pick a class, and stat accordingly.

I'm maining scholar for dungeons and group content, with SMN for soloing etc. So I put all my points in MND, and don't give a crap if my summoner has a bit slower dps when I'm soloing. It's all you can do.

It will be less of an oddball later I assume when more than one class has multiple jobs, and you'll have to stat accordingly. As of now, arcanist is the only class with multiple jobs like this.