Oh whoops! I think I misunderstood you
No you cant use his trait while getting hit by a combo although if he uses the trait as you hit him , it can still trade and you get grabbed. For example if ever sees you in RMS then he might as well go for grab cause it can catch you and any of your followups. Also the grab will hit before armor frames or active or after. Just random timings you have to worry about. It has happened.