I read somewhere that Heroic Mode would be available for Dragon Soul raids day 1 in 4.3. Was I imagining this? If not does anybody have a source? Thanks!
http://eu.battle.net/wow/en/forum/topic/2996319777
That may have answered my question. Looks like in a previous PTR patch, the LFR achievement for clearing Dragon Soul, "Fall of Deathwing" was what you needed to enable Heroic mode for Dragon Soul. Now you need "Destroyer's End" to enable Heroic mode, which is only obtained from normal mode Dragon Soul.