I still haven't installed tactics, but I HAVE done improved Abazigal during Ascension and Tamah (his girl) is a purple dragon.
Now I don't know if your purple dragon is anything like her, but keep the following in mind:
Tactics dragons use natural resistances combined with spells for 100+ resistance on everything. So if you lower
Magic Resistance and cast ADhW for example you will still heal it because it has 125% resistance to
magic damage
Talk about cheese
