Maximogu of Firetree posed the question "Why bring a Rogue to an 80 heroic?" in the general forums. He claimed that at this point there CC is unnecessary for most tanks that rely on AOE. Most of the trash pulls are handled by AOE classes now, making the Rogue's single target focus obsolete. He argued that Rogues are best suited with Druid tanks that do not handle multiple mobs as well as other tanking classes do.
Here are some of the reasons given for bringing a rogue along:
Anushka of Kel'Thuzad: There's a lot of nasty things that can be interrupted in most heroics. Though I wouldn't take more than one rogue.
Khadros of Frostwolf: To listen to the sound of theirs daggers going schlick schlick schlick.
Morgrimm of Korgath: Because one of my friends is a rogue.
Owari of Frostwolf: To DPS, of course.
Mypetgoat of Bladefist: It's one expendible DPS that won't roll on my gear.
Madia of Maelstrom: They need loot and stuff too.