The best tactic would probably be using the search-function though ..
as many a great strategy/tactic has been beautifully written down atleast a few times. Really, I dare ya .. type in Draconis and be overwhelmed with stuff to read [img]tongue.gif[/img]

Firetooth crossbow is great against him.

I could kill Draconis with major probs, but I killed him, and i couldn't even HURT Abigazal, as when he went dragon, game end.
I say bombard him with spells, pick off the stalkers all the time, keep your party alive

Draconis was fairly easy to beat.
If you have DragonSlayer it shouldn't be to hard.