"Since tamed greater dragons have maximum 1000 HP when undamaged, the maximum damage they can inflict with a firebreath against 70 fire resist is 30"
Wrong.
Last night while messing around with my new guild at Yew Gate, we were constantly being attacked by a group of 3-4 people who cheat up a storm. One of them, an Archer, can do AIs in a full out run every 1.25 - 1.5 secs (Like a Moving Shot+AI), can re-equip his bow as soon as you Disarm him, and can spam 15+ AIs in a row, without getting the Mana Cost penalty for chaining them. Not even my Mage/Archer with 120 Mana/7 MR/40% LMC can chain that many Specials.
Well, just to piss them off, i logged on my tamer, put on my Resist/DCI suit, grabbed 3 Bolas, and took my Fully Trained 951 Health Great Wyrm out of the stables. Went to the Yew Gate and Blessed/Invissed (Over 1k Health when Blessed) the Great Wyrm, invissed myself and readied a Bola. Had a guildy lure one of the guys over, i bola'd him, and sicked the Great Wyrm on him. The guy took a Claw/Bleed hit, and started running away...he almost got away but the Firebreath took him in the back for 75 damage. The guy took a dirt nap. Then the Archer started attacking my Great Wyrm, sicked it on him, pretty much the same thing happened. Bite+Explosion, then Firebreath hit the Archer when he was barely off my screen for 70+ damage, he bit the dirt too. Then the Mage FSed me for 22 damage, which i easily healed, and i sicked the Great Wyrm on her too. She was running and trying to Paralyze my Great Wyrm, which didn't even hold him at all because of his 117.3 Resist, she ran past a house, and cast a Wall of Stone between the edge of the house and the ocean, but there was just enough of an opening for my Great Wyrm to hit her with a Explosion+Firebreath, she dropped dead too. Then i sicked the Great Wyrm on a blue Necro/Mage in Wraith Form of their's that was attacking a guildy of mine, he dropped in no time.