As you know practically all bosses in 5 man heroics five from ~75 to 150 rep (+your bonuses as human and guild rep bonus).
But in Shadowfang Keep there is not optional 2nd boss which is often skipped by many players ( Baron Silverlaine - NPC - World of Warcraft). After his death you gain 500 rep from tabard on you and + 500 rep with your guild.
It is going to be fixed soon. -enjoy