I agree that the AC Perry heavy nerfs seem uncalled for, especially considering Arctic Troopers comparatively slight nerf (he's still very good in PvP and was always 10x more prevalent than any engineer variant). Engineers in general will never be that great as long as they are the fattest 125 HP class and stuck with horrible weapons for most of their variants.
As far as Corn, the entire class is fraught with problems because it was a bad idea in the first place. Taking Foot Soldier and making him a big target but giving him extra HP/ammo is just lazy design. The corn feels overpowered and underpowered at the same time because his abilities have insane damage potential but are unreliable and clunky as all hell. This just leads to players just spamming all three abilities as one or even two may not get a kill, but all 3 usually will. I'm honestly not sure what to do about him, though a further nerf to HH (reduce the damage or disallow steering) while making SS a single missile with twice the damage would be a good start.