I killed the dragon like 3 times. 2 times in one game (I thought I could use less items and save them because I was sloppy), and my second character (the thief). The second time I beat it was on Nightmare difficulty, this is what I did.
My tank is like level 14, or was 12-13 at the time I beat it. Heck I saved right before so I can fight it again whenever I want. Loading up to check stats (lol I'm talking like I'm posting this live).
While I wait for this to boot up, I take it that Mefya hasn't fought the other dragon yet? This dragon he's having problems with is the hardest. The other one would have been good to practice on.
For the fight I basically made sure the tank did Threaten, Taunt, and Warcry whenever possible to have hate locked on him tight. My tank has Shield Expertise (no shield mastery at the time, that would have been a lot of help). Anyway I tanked it with a human, Shale is the better tank (the rock dude), but I just don't know how to use him.
Tank level 14
313hp/195stamina
Rogue/Assassin 15
I was eating his back side up with crit/backstabs.
Rogue archer/bard 15
There is this ranged shot talent called Arrow Of Slaying that I used whenever possible. That thing hits hard but I still miss a lot.
White mage type mage.
I have the mage and ranger far away while the tank is in the front of the beast, and the melee rogue is in the back critting/stabbing like a mad man. The tank drinks that fire resist drink cause he's the only one in breath area. I have a lot of physical attack resist from runes I installed on the sword, and the helmet so I don't get knocked on my back. My curemage keeps his hp above 80% because the real tank killer is that grab the dragon do. Cast reraise on the tank if he gets grabbed if possible. It's called Life Ward. I also made a lot of potions because the mage timers are always down. Wynne can make low level potions by default, but if you put another point into herbalism you can make better potions which is best.
I'm sure Mef got the position of characters in a good way but here's what I did. (while taking these pictures I didn't cure the tank. HP should never be as low as seen in some of these)
Resisting a knock down
So the fight is all about keeping the tank alive. Mana drinks for the mage, Cleansing Aura, and that Vessel of the SPirit ability you get with Wynne (get a lot of respect from her). Lots of normal level potions. Maybe lesser level postions for the melee guy (if you can get 2 rangers, one mage, and one tank that might be good too.
Edit: For my tank's armor
+20% mental resist
+60% physical resist
+1 willpower
+5% Spirit resist
+2% spell resist
+20% Fire resist
+10% healing effect
+6 Def
+30 hp
+50 stamina
*High chance of paralysis (weapon buff via rune)
*High chance of slow (weapon buff via rune)
*My armor total is 31
*Defense total is 74
*With fire resist drink (lesser balm drink) my total fire resist is 50%.