No, hes annoying as he is with the debuff reflect and mystery

He's strongest in fox, with ninjas like shisui he's a beast

In my opinion, fire main is not the weakest .. Actually, all class is fair and all strong .. The strength of each class depends on the player itself .. I can't explain it well but lets put it in another scenario, it's just like .. You have a great sports car Koenigsegg, but you drive like your granny .. get it?

shield that gives your entire team debuff immunity, permanent debuff reflect, clone that gives you double standard attacks. Nah the fire main is fine, in fact he's probably the most used end-game main.

out of all the mains, water is the strongest cause of poison aids, fire is second strongest

Fire is quite strong if you running your team has only (or the majority) event ninjas. If you are only using ninjas from treasures, then fire is the weakest (or at least tied) in terms of how other mains can create better teams with just only treasures.

In my honest opinion Scarlet Blaze is currently the strongest and most annoying main, but to make him work you require a whale lineup (like, for example, shisui-madara-itachi susano'o).