At level 70, run speed is a very valuable enchant. There are various options for run speed; meta-gems (both crafted and vendored), trinkets, enchants, even a level 62 weapon. The speed effects don't stack; you can only have one run speed available for an extra 8% speed. There are lot more options when you're outdoors, but those aren't relevant to 95% of raiding.
Of the options available, the best bet is enchants. Cat gear should be enchanted with Cat's Swiftness, bear gear with Boar's Speed. These enchants aren't cheap; 8 Large Prismatic Shards plus some primals. And they have a tradeoff compared to other enchants; you're giving up +6 agility with Cat's Speed and +3 stamina with Boar's Speed.
But you gain more speed. And pretty much every single boss fight in raiding requires melee DPS to move. Get out of the fire, or run from the whirlwind, or chase after the mob, or something. You pretty much never get to stand still and attack. So when you need to move, an extra 8% speed is quite useful.
PS: it's a silly title, but Faster, Pussycat! Kill! Kill! is actually a fantastic movie. Go watch it.