Cwdt or cws +Immortal call questions

I have played many characters which use the combo of Cast with damage taken and immortal call, I have always wondered if cast when stunned might be better. I am also wondering if it is better to keep them at level 1 to cast more frequently or if there is actually benefits to leveling these gems even though it seems that cwdt won't trigger as much.

Could someone shed some light on this.

CwS isn't reliable against things that rapid-fire you to death, and doesn't really have any upside in this particular case.

The benefit of levelling CwDT is to allow you to trigger higher-level spells with it. This is totally irrelevant for IC because all that levels do for IC is increase the duration per endurance charge. If you have no endurance charges, level 1 is as good as level 20.

Thanks for the clarification. I am running this build with endurance charges since I use enduring cry.