As a lurker I guess that's the best this iron dragon can hope for - try to engage the PCs while Iron Wing Defense is up, then get out of combat until it recharges and re-enter the battlefield in an advantageous position. Seems pretty lousy to me, unfortunately.
*edit* Although, if you give the iron dragon a good environment for sneaking I suppose he could fit the lurker role well enough. Say, something like foggy tunnels or thick forest, where he can retreat to total concealment & make Stealth checks. Still underwhelming...
I like the warforged resounder! He seems more like a controller than an artillery monster but I like him all the same.