Difficulties with adds on Rag?

Normally, I can take out my add just fine but sometimes if it spawns right near the hammer, I have some trouble. My AB hits for anywhere between 16k and 150k, so sometimes it gets 1-shotted and other times 4-shotted. As a mage I don't have a reliable stun and my slows/freezes don't work. What's a good rotation for getting these guys to 50% health almost instantly before they get anywhere close to sulfuras?
Rotation is obviously AB spam. Unfortunately you won't be able to have any stacks up as even hitting on Rag before they spawn it drops off before just before they spawn.

Only thing you can really do to help out is save a Pom so you can pom/ab right away on the closest add you are working on. I found for my mage I could even take down one right next to the hammer, though it was really close. If you are on an add at least one further out you should be fine. To be safe just make sure you have people with stuns getting the two closest adds.
If the hammer lands near your target add, keep ABing Rag as long as possible. When he's gone, use Presence of Mind and pop the insta AB on your add. You should have all 4 stacks at this point, so murder that add ;)

Also, you may want to consider holding off on a second round of CDs in phase 1 to save it for your add. You may lose some dps overall, but it's better than 0 raid-wide dps ;)
If you get an AB off with .7 seconds of Rag going into the lava, you will be able to keep your 4 stack. As a safety precaution, keep your Presence of Mind cooldown in the event you dont get that last AB off on Rag. Pop PoM on your burn target and you will be back at 4 stacks. :)