7.0 (Legion pre-Launch), Blizz ninja nerfed Speed to 110%. Any added Speed (as Tertiary Stat) past 110% is hit with DR. As an example. I had a nearly full Speed set on my 100 DK back in WoD and he sat at 184% Speed. As soon as Legion hit that dropped to ~134%.
For DH you want as many pcs with Speed on them (even with DR) and MAX Mastery. Like spammy mcspam Mastery everywhere possible. Also, get a pair of iLvL 600 Boots from Skyreach with Speed (it may take you a while) then Enchant them with Minor Speed, THEN upgrade them to 610 2/2 with Valor. You will retain the 10% Movement Speed Enchant and gain another 1% Speed from the upgrade, before DR. Lastly, the 10% Minor Speed and the nerfed 2% WoD CLoak Enchant still stack, even with Legion's DR to Speed.
Last thing, you want the 101 Food that gives you a Movement Speed burst for a short time after each kill. The Legendary Boots are obvious.
