not to mention you can get dry spells of just getting nothing. I did 17 Mythic+ last week and only got 1 dropped piece, if it wasn't for one guy who gave me a cloak that's all I would have gotten for the week aside from vault. It's just not rewarding.
If at least 14 of them were timed and all in the m+11-15 range you now have enough wyrms to craft 4 additional 437 items to complement your new cloak.