I believe the Zagan part is the fight in the cave right, nest dais and one flying enemy but if you wait too long the nest will let out too many other enemies to fend off attacks from. What I did was basically just throw down a potion and go in close and use flaming breath on the nest right away try to rotate around it as your breathing on it to avoid attacks from the boss. Once you get it down try to get some distance between you and the boss and recover however you can potion or skill or both. Then just launch fireballs and keep your distance specially if he starts to glow like he is going to do a burst, if he gets close unleash your own burst and just keep the fireballs coming every 5 seconds. That's the only place I ever died in dragon form but its definatly beatable, key part is taking out the nest and recovering, the battle begins after that. Helps to max out your fireball skill at least, healing skill not a big deal but one point to aid healing helps, burst max is you have plenty of skill points to throw around.
