Why not? These epic gems don't make older gems obsolete, as you'll still need the +50 ones to craft the +75 ones. They're also not "incredibly difficult to obtain" (personal opinion). Mythic dungeons =/= Mythic raids. And getting rank 6 in Brawler's Guild is doable at ilevel 615 if you're good, and a complete walk in the park if you're at least LFR geared.