When you fight Jad, try to use range and don't stand next to him or he will use melee on you. You will need prayer, as this will block mostly all of his attacks.
When Jad jumps up, pray magic, he will shoot a fireball at you.
When Jad slams the ground with his legs/paws/hands, ect, pray range, a rock will fall from the ceiling.
Jad does currently drop a firecape.
Good luck and happy hunting!