I just used Emergency Power to Shields 10 times and it hasn't proc once. This cannot be just bad luck because even my green version procs more often than that. I have a hunch that the reduction of the blue quality and higher is negated because it cannot go beyond the global cooldown. Hence, the reason why only green and white quality works. Recommend setting a flat value of 30% cooldown reduction and keep the chance to proc the same.
The purple ones proc just fine, I tested it myself just now. They do not, however, seem to have that 35% proc rate. Maybe I'm just extremely unlucky, but after forty activations of Emergency Power abilities, the proc rate seems closer to 20% for me.
Edit: Hmm... adding a blue doff as well did nothing to raise proc rates. I there's certainly something wrong here.
The duty officer active power was recently modified as noted in the patch notes to always reduce by the same amount - 30% - at an increasing chance to proc as you get better quality duty officers slotted. This was done because the higher reductions by quality were in fact running afoul of the global cooldown.