Dragonrider’s Compassion does not appear to increase speed for Feral druids or perhaps characters who have > 100% run speed. In my case my feral has 115% run speed without the Dragonrider’s Compassion buff, and once I get the buff with 10 stacks to give 10% movement speed it still shows 115% speed, and there is no noticeable increase.
This is determined with the following macro:
/script base = BASE_MOVEMENT_SPEED
/script cur, run, fly, swim = GetUnitSpeed(“player”)
/script ChatFrame1:AddMessage(string.format(“Your current maximal speeds are: running %g%%, flying %g%%, swimming %g%%.”, run/base100, fly/base100, swim/base*100))