I have a Fireface UCX which I am very happy with, but found the front facing LEDs were bit annoying; especially the flashing "MIDI In" lights.  My universal fix for bright LEDs is to put one or two layers of coloured electrical tape over the lights to lower their light output.  For the UCX I have placed two layers of red electrical tape over the four "MIDI In and Out" lights on the right. This way, I can still get the optical feedback that everything is working if I look closely but it doesn't distract me at other times.

This works on my pedals and amplifiers as well.  Especially those pesky bright blue leds that were popular for a while.  It is fun to experiment with different colours combinations.  For example, Red tape over Blue LED, Yellow over Red, etc.  This fix is certainly cheap and is easier than changing resister values.  It seems to last for years.