Woah finally I can get out my hate for the Eva 8. Lets begin.
Eva 8 for all the glory and rounds it can hold is amazing. However, with the changes to only be able to stack 16 shells, it kinda makes the gun useless further into the game. As 2 clips and you're already out of ammo or have to carry 4 stacks or more which takes up a lot of space for other items or ammo. Not a good gun to really use unless you plan to swap out later.
I wish they would change the ammo stacks to at least 20-24 to make a shotgun worth carrying and spraying.
Havoc to me is in an all around good spot. Early game the gun is amazing at putting down enemies who pick up a gun with no attachments. If you can control that recoil even a little, it becomes something deadly and not something an enemy wants to hitting them for too long. The two hop ups it uses are amazing given you pick up a extended mag or some sort and a scope you're comfortable using.
My overall favorite thing to do with it is carry both hop ups and a basic x1 scope so i can go from sniper to AR in an instant. There is no bullet drop that I can see when in single fire so it's an amazing feeling when you hit someone across the map all by lining up your cross hairs perfectly.
If I was to suggest any change to the Havoc, it would just be to extend the magazines a bit more. It runs out fast with a turbocharger and without the charger, you're missing half those shots trying to build up the speed for the havoc.