Mezs are 8 sec, standard stuns are 4 seconds, carbonize is 2.5 (3 with set), jarring strike knockdown is 3 sec, force push and spike knockdown is 2 sec. Knowing these durations, and mentally counting GCDs is part of the skill. No other class knows their ICDs and a lot of classes have them. PT Pyro must now deal with it.
Utilizing auto-attack, thermal det, DFA (I understand this is a target of opportunity thing, but you can force a carbonize--> DFA) within that window will net you more damage than someone who doesn't, again raising the skill cap of the class.
Your suggestions are:
Showing the ICD (which no class gets)
100% proc (which dumbs down the class even more than it is)
6 second rail shot CD (see above)
Only showing the ICD keeps the rotation more fluid, but it also lowers the skill cap.