This is exactly same conclusion I have reached. I don't think its really worth it to summon AotD for Icehowl. If I would be inclined to use it for Northrend Beasts at all, I'd summon it in the very beginning of Jormungar to burn Acidmaw down really fast... Or even use it in the start against the first beast and have it ready for the Jaraxxus again.

On heroic Beasts I use army right at the start, as soon I get the message 'In combat' I start channeling and I can get both army and ghoul up before Gormok is targetable.
Why on Gormok? Because it still feels the hardest for us, even if we 2 shot it now.

Unless you have really high dps there's no time to summon army before Acidmaw is engaged. Also if you have good dps to burn Gormok before worms start to enter, then you can just as easily burn Acidmaw to 30% before he burrows, and finish it fast afterwards, so no need for the army. I'm not sure how much can army survive from the green shit on the floor, and from flame aoe.

This thread may be deprecated and if so then feel free to ignore this post.

I've been working on a new MMO project and haven't been an active WoW player in several months. If anyone feels the need to maintain and revise the summary, or create a fresh one with the most recent information please feel free.

With any luck I'll get to see some of you guys on our own forums at some point in the future.