You should ask him. Or read the blood threads here and learn a few things about how to gem.
Hello. I have a question regarding blood DK.
I checked Riggnaros profile (US-Blood Legion) and it seems that he's gemming for mastery as much as possible. This seems interesting to me, because so far I stacked stamina all the way. His progress is impressive and he's probably knows what he's doing. Is it worth to gem this way with full 359 tank gear, or it's better to stay staminatank until I'll swim in 372 epics? Or is this kind of gearing suitable only for some heroic bosses?