A level 3 Ranged or Artillery Tower with a level 2 Melee towers pinning them is a viable tactic. Status towers can also help to reduce their defenses.
Isolating them from other units with melee at a certain area also works nicely because the towers will spawn more than they can kill. It doesn't work if the Pilots are backed up by Vanguards, Bowcasters, or if the Pilots come in a large amount.
In extreme and in events Champions and level 3 Melee Towers will lose in a 1v1 fight, so its best to make sure they are supported by other towers or with orbital bombardments.