Honestly I dealt with projectiles in the past by walking > powershielding > walking. Chronopenguin's post is basically all you need to do. If it's something like Link's bomb in the heavy mix, then SH airgrab those things & throw 'em back, Mega Man's Metal Blade style!
Edit:
Nair is a nice move to deal with projectiles, so is Fair but to a less extent having more risk due to it's landing lag.
Character-specific, Toon Link is definitely going to be a LOT of walking > PShielding > walking. Listening to the SFX of his moves may help so that you know exactly when they're shot / released / fired. Boomerang can be avoided & then VIsion proc'd as it comes back to do either the regular or Forward version. Never airdodge the projectiles unless it's for catching them airborne high up, or if you SH & airdodge them at a fair distance away that isn't punishable.
Robin's Arcfire is based on a Mana system so you have to keep track of what types of Fire moves he inputs to know when exactly his Fire Tome SideB will vanish & go on cooldown. So for now because Shulk is outranged by Arcfire that can hit on-shield, it's safer to either Forward Vision past the fire to close distance, given that you're fairly away from Robin to avoid a punish of any kind. The other & more safer option I've done is just to wait right in front of his / her fire. If you have Speed on, you're going to dash through that dying fire like it's the signal to GO! at the starting line. It's a race
Mega Man is interesting because people get scared of Crash Bomber & put up their shield holding it for a long time when you don't need to. Simply know the count-down timer when it explodes once it sticks to you, & put up your shield around the estimated time it will detonate. A ballsy & daring approach option is to rush in to Mega Man with the Crash Bomber on you, & Vision counter having Mega Man nearby to be within the "Zone"'s reach slowing him down, & punishing him for it.
