There's been recent tests over at BG that prove the DPS difference between a controller user and a KB + Mouse is negligible at best, if it's even there. Basically, if you missed a single cooldown on KB + Mouse you'd fall behind the controller user who doesn't, and never catch up. The whole line of KB + mouse being optimal is really just bias with regards to this game.

The controller support is very, very good in FFXIV, and it's only getting better.

Personally I'm on a PC and use a controller because I find movement and camera control way better with a controller. I also use a KB + Mouse all day at work and prefer not gaming with them when I can.