Yeah, the dungeons layouts are disappointingly linear. Almost as linear as the entirety of Final Fantasy XIII. I think the only dungeon that's slightly less linear than the rest is Toto Rak. If I remember right, you have a choice of which path you can go down, even though they all lead to the same destination and lead to the same boss in the end. I think even 1.0 had non-linear dungeons with Cutter's, Aurum Vale and Toto Rak.

I wouldn't mind midcore content designed to add exploration to dungeons. The bosses are fun albeit easy, but the trash and dungeon layout are always the same.