So i’ve played this game a whole bunch at this point and pretty much focus on banished because I enjoy playing them a lot more than UNSC. Right now i’m really lost in the cutter match up vs banished. His tier 1 is, in my opinion, much better than banished if your opponent can micro away from suicide grunts and jump to the grenade throw early you really don’t have a chance. Then at tech two a mix of cyclopes, marine/odst, nightingales, and air/snipers is super rough no matter what you throw at it. Then even if you manage to have a better army build his drops are savage. Obviously with ship you can just hide and teleport locus everywhere which is still viable but besides that i’m not sure what decimus or atriox is supposed to do to counter his early and mid game. If anyone could just throw any suggestions at me i’d be grateful.
Cutter is a really solid leader, so don’t feel bad struggling against him.
As Atriox when you’re playing a Cutter you’ve gotta take advantage of Dying Breath on your Suicide Grunts. It’s a great way of making sure they at least impact. Mid game you should use Bulwark/Dying Breath and Teleport to help give you an advantage.
I’m not much of a Decimus expert (still learning him, I confess) but I know Vortex combined with Killing Frenzy will help you a lot in the early game.
Hope this advice helps!
Edit: Nevermind, saw you were a Champion. My advice might not be as sound 
Grabbing those mini bases before Cutter is probably a must. It might even disperse up the army too. I honestly believe cutters micro at tier 1 in the right hands is the meta for 1v1. The best thing to do is to prevent his army from getting to your base. However, once the nightingales arrive it’s pretty much over. The only solution I could think of is making small groups of brutes/berserkers to attack mini bases and eventually his base. Damaging cutters economy would hurt the leader powers and make cutter face a choice. Defend the base or focus on the attack. Unfortunately, at that point he could probably make a sniper or bell ringers at base to defend pretty easily, but it might but you time to get some suicide grunts to hurt his attacking army.
You’ve actually pretty much listed exactly how I play cutter. My best bet would be to use support powers as a counter for the unit drops. Keep your glassing beam and your bigger offensive powers in reserve for clearing out the reinforcement drops if you can survive into the mid to late game. After that all you have to worry about is having a better head to head force against the infantry combos.