You can't fix it, simple because there is "NOTHING" to fix when the ability was changed (/cough nerfed /cough I mean "TWEAKED") in the original game code provided by TC, introducing a fictional global cooldown to it, just to annoy hunters... Oh!... I mean to "Balance hunters" ofc... Just wondering what does stands "FOR" "Instant Cast"... Btw, this ability should not affect entire team, only Master & Pet, and should not be on pet gcd, what a curious coincidence..., like the coincidence with howling... right? xD /sight.
Still there is way to bypass this "tweak" and secure the ability proc using a simple macro with and a conditional... lol...; just a tip you need to be redundant whith it.
PS: I assume you guys are talking about CotW.