If you go to Grimoire then goto Activities and then Raid then click on the second one, at the bottom it tells you your total raid completions.
How many do you have?
I'm at 46
EDIT: I've had multiple Hunters at one point so if you try to add up my Raid completions by looking at my characters the numbers don't add up, but if you look at my Grimoire then it shows the real number
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47 and cant get a helmet.. Yea I know, it's sad. But i did see a level 26 get 3 of them..