A dragon doesn't need to get into a protracted firefight to do the kind of damage Remik describes Stabbey. Especially not in Skirmish mode. And to hell with research points on skirmish and bigger campaigns. Those 60 research points will help the dragon to often do far more than 60 recruits of damage, over and over and over and over and over.
Pop up > Jetpack into the middle of a Land-based army > Fearlock everything with roar > Dodge the few missiles they manage to put up > Pillar of Flame > Run away!
Price of summoning dragon: 20 recruits. Free if it survived. Possible every minute.
Results: 600 recruits worth of damage if player produced a lot of AA. AA units are usually the most fragile and targeted ones. Groups of hunters and grenadiers go bye bye in a patriarch strike. Damages will take 4 minutes to rebuild with a single factory.
The strike itself however, takes about 4 second, which is quicker than what it costs for most AA missiles to even reach you.
In multiplayer, the dragon in the hands of capable players, does completely dominate the battlefield regardless of your RTS abilities. My counter strategy is this:
http://www.larian.com/forums/ubbthreads.php?ubb=showflat&Number=472730#Post472730Neither Patriarch nor pillar, work on sky units and as you said, imp fighters are the best AA. If they want to dragon attack my Sky-based army, they need to content with the fighters. Just be sure to spread them out so they don't get feared.
I propose putting the one-hit abilities on a far larger cooldown to get what you want Remik. Patriarch and Pillar, should take at least 5 minutes to recharge.
When that happens, these skills become panic buttons only and we'll see a more prudent use of the dragon. Stabbey's dreamworld will happen, where dragons are forced to fight normally, get distracted and AA works again. I'm also accepting of making the dragon more expensive, the skills costing recruits, or making the dragon and its innate attacks stronger at the cost of nerfing its skills.
