Originally Posted by
Lothrik
Maybe yours don't, good ones do though. You only actually need high Mastery for a small handful of fights, high Haste is vastly preferable on most fights, speaking as a healer in 10M here. Blood DKs that stack Mastery on progression 10M fights with tight DPS checks are just crippling themselves and wasting their guilds time by doing so.
Edit: Just for comparison, the two tanks in OP's parse were pulling 96K and 75K respectively on their 18th H Jin'rokh attempt. Our tanks gear basically exclusively for DPS and our MT pulls 291K~ DPS(e) as a DK. It's a completely different mindset going from a Mastery DK to a Haste DK.