I generally use traps etc... I didn't make a single potion for a long time untill i noticed i had 154 elfroots... had plenty of poultices after that.

Anyway taking out any of the three dragons was a bitch for me because of two reasons. First play through I was rogue Duelist/assasin (IMO the best 2 specs for rogue) and my group makeup was the same throughout the game once i got the characters: Wynn (healer) Morrigan (crowd controll spec) and allistair (tank spec with all tank gear and only constitution with minor strength)

Now the reason why these two things were problematic was... as the rogue I would have to get up close near the rear of opponents to do major damage... well dragons don't like that and they give you a good ol' fashion kick in the chest for 100+ damage everytime you get close. So that made me use range, which even with special arrows (i think the arrows are the reason no runes are alowed for bows) I was only dealing about 30-35 damage per arrow shot.

Unfortunatly all but the arch-demon (in my experience) would bite and hold onto whatever character was right infront of them and do massive damage before you could get them free (on normal even except for cone of cold Its super hard to stun them unless you have high magic).

All of these things pieced together ment... I was doing hardly anything shooting arrows while Morrigan would have to save mana and only use cone of cold while Wynn auto attacked and healed allistair if the dragon got a hit in or not. If Morrigan was resisted or worse... ran oom (out of mana) Allistair was quick to die... followed by me because even though when fighting dragons I wore high magic resistance gears the physical damage massacred me. And even if wynn got the rez up it didn't matter.