He retakes Thunder Bluff from Magatha, warns Theramore of Garrosh's attack, covers the Horde's retreat from Theramore, saves Garrosh from quillboar, organizes the retreat at Lordaeron, coordinates the Horde's efforts with the Zandalari on Zandalar, and rescues Derek from his cell aboard the Horde warship. I'm pretty sure he's done more than Cairne at this point. Now, if you want to argue he's disloyal to the Horde, that's fine, but saying he does very little is a gross exaggeration, particularly when compared to some other lore characters (Zen'kiki is my nomination for most useless).