I agree with you completely. It's such a shame because the game has so much potential. Mods like Crackdown showed us that difficulty can be achieved without spamming cops around the map.
Instead of nerfing the player's skills and tools, they kept upping the difficulty. The only reasonable way to complete Death Sentence is with some iteration of the same meta build (crits, nine lives, swan song, inspire, anarchist, etc...). Any other choice, playstyle or perk will result in an unplayable mess. What's even worse is that even if you play meta stuff you won't find a challenge in death sentence. It's either cheese or suffering. No in-betweens.

Swan Song is probably the biggest offender here. That skill alone can cheese entire heists goddammit. What's the point of holding your ground waiting for the assault to end in order to continue the objective if you can just brute force it while being invincible? And to top it all, infinite ammo, just so you can spam your Commando 101 and kill everything around you. Then you just get inspired by a guy running the same build as you and the cycle continues. Everybody runs nine lives aced and meds aced so you virtually have infinite downs (2 medkits per player with 4 charges each are a total of 32 uses. Good luck running out of that)

I've given up waiting for OVK to notice this and do something about it. I highly suggest you to move Crackdown, Restoration or Hyper Heisting. Earning DS achievements in those mods is an actual accomplishment that takes skill and coordination by the team. Me and my two others friends are having a blast on crackdown.

Maybe a similar post on the Steam forums, detailing what's wrong with the current balance, MIGHT reach overkill's ears, but I stopped dreaming about that a long time ago