I don't main TLink but I play him. If you know he's gonna d-air, bait it out and attack after he lands. It has a decent amount of landing lag so you can punish him accordingly. His u-smash is something you can just bait out as well if you know he's gonna do it. He's vulnerable while pulling out his bomb and high chance will be if you approach him, he'll throw it at you. So you can either spot dodge, roll, or block, and grab the bomb to throw back at him. You can easily guard and jump over his arrows and boomerang. I recommend blocking the boomerang and not dodging or spot dodging. Why? Because it comes back and can screw you over if you forget about it.
There have been plenty of people I've fought online that's been able to get pass my projectile game, so he's not op. Maybe you just need some practice against someone on here that uses TLink to help familiarize yourself with him.
the bit in bold is essential.
i main link/toon link and i can't tell you how many people i KO because they forget about the boomerang.
with link the gale brings them close for an unsuspecting smash
with toon link the damage from the boomerang return gives an opening for a strong smash
most toon link players won't bomb-cancel with his Dair and the lag on that it painful in a fast, closely-matched game.
toon link is by no means a strong character.
he can tot up damage with his projectiles if you aren't careful, but his dash attack is not a finish (like link's is).
if he gets you to high damage, beware of his backwards throw; it KOs at 100% or higher if you're near the end of the platform.