The only useful part of Tibbers is his initial cast
Other than that, he just kinda lumbers around and bitch slaps people. I think maybe he should be a passive and not an active. So like, when you unlock your ult, he spawns to fight for you, and he has a 30 second respawn time. You can activate your R to make him appear somewhere else in a blast of fire (what the current ult does), that would be on the current cooldown of the current ult. And then he could maybe be considered another champion, because to last until killed, he should have improved defensive stats, and maybe a bit more AA damage.
So I'm just asking for Tibbers himself to become more useful other than an AoE spell that spawns a temporary, bitch-slappin' bear.