I know reflections can reduce FPS but not by 25/25%. It can increase the number of things to draw by 100% for sure if it's done as a true reflection, but even then the performance hit on a modern card with FFXIV's graphics would not struggle - just look at games like Crysis with reflections and we can run that at 60FPS+ on modern hardware.
Also, years and years ago I used to mod for Star Trek: Elite Force and also Jedi Academy which both could do true reflections (including characters and their weapon effects) - and that was back in the 280 days!
http://i.imgur.com/an05rTT.jpg
Basically: give us an option to chose the performance hit ourselves because those reflections are ugly!