Theyre nerfing it because of the new heroics.
The only people that will be doing older heroics are those that are still gearing. Its not hard at all to get 346 ilvl, and of course that means you'll never be doing older heroics again most likely. Its just more so that when u get a group of fresh 85s in terribad ilvl 329 gear, it isn't still a wipe fest or anything.