DBS, PP, BQL and Sindragosa should all be done in heroic, however, doing a fight in the HC mode locks you to that raid and you can't switch it back to 25m HC or vice versa.
Hence, unless it is bugged you need to run ICC25HC to access LK25HC.
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Tanking with the Blessing of Kings - The TankSpot Guide to the Protection Paladin - Updated for Patch 5.4!