Courtesy the amazing Quick Armory.com, these are the heroic achievements I have remaining:
These achievements are:
3 in Drak'Tharon - but all three easy - I just haven't been in ages, or haven't been in a group that wanted to do achievements.
Consumption Junction - Quite easy if you know what you're doing - just have to hide behind pillars to prevent his stacks from reaching 10.
Oh Novos! - Even easier. Just really no skill involved. Just keep the stairs clear.
Better off Dred - Heard it's easy, I've just never even attempted it. I should be able to get these three in one simple run.
1 in Gun'drak - Less-Rabi. Takes a lot of luck and some perfect timing to get those last transforms from going off. Hopefully we'll have an attempt tonight at it. He's quite easy to get to in the instance.
1 in Culling of Stratholme - Zombiefest! Another one that I heard is easy, but just takes time and most groups want to plow through for a bronze drake. I think we all have the drakes now, so it shouldn't be hard to convince a group to do this one in the future.
1 in the Nexus - Split Personality. Another one that just takes luck. The last time we attempted it, we easily did the first split on time, but on the second one, one of the images was just barely outside of our AOE and she didn't go down fast enough. Shouldn't be too hard to get.
1 in the Oculus - Make it Count. According to the comments, it's not too hard to get - just have to have a focused group that won't wipe and can quickly move from platform to platform without having to kill too many drakes in between.
1 in Violet Hold - Dehydration. Figgy says this one is easy to get - I've tried to time the pulling of the levers to kill the blobs before they can merge at all. I think I'll just have to go with her and leave it up to her to pull the levers at the right time.
And then I'll be done! (well, except for the new Trial of the Crusader ones - but those will just take time)