I have been loling around 12/12 normal mode past few weeks since we are gearing up a new raid team consisting of our old WotLK raid team and people that have no raided for years (Basically people were at 480 item level 2 weeks ago), so we are gonna start heroics next week. I was gone for vacation for the first months of 5.2.
DP > HA at 25% haste presumes you are tanking 100% of the fight and that the fight duration does not increase/decrease the uptime of HA. Like, say you got a fight with a heavy damage phase every 3 minutes, then you will use HA every 3 minutes instead of 2 minutes. If instead you have a fight that lasts 3 minutes (Jin'rokh hi), you can use HA twice making its uptime far higher than the average.
I still do not like HA as a cooldown. I prefer DP whenever I do not need a cooldown and SW whenever I need a cooldown. DP gives more dps. I like dps.