15% bonus on RG is no where near enough to make it viable for raiding. The proc is random, so those RG's are just as easily overheal as a poorly timed Flourish (whereas with flourish you control the timing). Flourish is still just a very strong option due to synergy with WG, Cenarion Ward, and Essence of Ghanair. And stonebark is still great for Mythic+.... Omen even with the buffs just still isn't competitive when it comes to raiding or mythic+