That is all well and nice, son - but you can tell such fairy tales to people who haven't played the game. You see, your strategy does not work on Adra dragon. My fighter tank with best equipment I could find gets annihilated by the Adra dragon in 2-3 blows. Even if I was able to heal my fighter - which I cant because your healer needs to get close and then gets crushed by the dragon before he can cast a spell - my fighter would still get annihilated 5 seconds later. Secondly, the range on pretty much any other spell is well within the reach of the adra dragon, so when he does his 360 degrees attack - he one shots anyone who is trying to cast a spell at him. To top it off, he is immune to everything, unless you can petrify him - but good luck with that (as I said spell range is the problem).
The only thing that works on him is to get lucky and successfully petrify him before he one shots your spell caster, and then quickly bash him to death in 10 seconds before the petrifying spell runs out. Trying to keep the aggro on the adra dragon is not possible, because your fighter will be dead in a matter of seconds. And to even compare Sky dragon fight with that green monstrosity is ridiculous. Sky Dragon is nothing in comparison to the Adra dragon. The only sure way to kill that green bastard is to cheese your way to victory. As I said, spamming infinite number of giants by your chanter while you are keeping your distance does miracles. She couldn't even scratch me - which proves my point. Crappy design.