[SixOfSpades]

The reason Draconis is difficult for your 4-Wizard party is because he keeps turning Invisible: You start casting your spells directly at him, but he turns Invisible while you're casting, so your guys lose their target and all your best spells are wasted. To combat this, you can either (as has been said) stop time (and have a True Sight running on the person who cast Time Stop), or use area-of-effect spells that don't need to be cast directly at the target....unfortunately, Lower Resistance is not one of those spells.