Direct damage is mitigated by armor, through a complex formula. Higher base damage means better armor penetration, which scales damage non-linearly. Azlar has a 6% higher base damage, so he penetrates armor better. Also, DOTs always do the damage amount they specify instead of being mitigated by armor.
So against a high armor team, Azlar will always do more damage than Quintus.
I don’t mess with Rigard, I’ll bring say Melendor and BT and just heal it away. It is a pain to have Rigard ready when Azlar fires. From my experience, debuffing the enemy is way more useful.
Though rumor says both Azlar and Quintus get passive abilities related to physical damage/ shield/ board matching, but one ability increases DOT ( Azlar ) and one slows enemy mana generation ( Quintus ). If the rumors are true when classes go live, you might use Azlar versus high armor and Quintus versus very fast mana.
They are saying he may have that ability once the class system is released. Apparently decreasing mana generation is one of the new “special skills” you can add to his hero class via the soon to be released training trees. All is still in beta testing so don’t bank too much on it until everything is released though.