Pally ret t10 2p bonus was changed from "chance on melee hit to refresh divine storm" which proc'ed Divine Storm! - Spell - World of Warcraft to "Increases all damage you deal by 5%.". This happened in patch 4.0.3, when they changed paladin's mechanics.
The key bit is that 2t10 still resets the CD on DS. This also resets the CD on CS, but it only triggers if you actually cast DS. On AOE fights where DS damage is really relevant this means that 2t10 is actually much better than any cataclysm option so far.
NOTE: It'll not work if you use crusader strike, so just useful for heavy AoE fights.