Games

It's an old game, but Pixel Junk: Monsters is a ton of fun as a co-op tower defense. Don't bother with the sequel - s'bad.

The Division 2 is fantastic co-op and often gets put on sale.

It's a very different experience, but have you considered Baldur's Gate 2?

Dark Souls 1 (remastered) & 3 along with Bloodborne are good options.

Not played most of the games you mentioned so not sure this'll be your thing, but I've gotten back in to Sky: Children of the Light recently and it's been great.

It's beautiful, f2p (ad free!!!) on a bunch of different platforms, and going in as a pair will give you a head start since it has a social aspect and is designed to occasionally get players to cooperate (though you can play alone just fine, I do most of the time and cooperate with and befriend other platers). It's mostly chill and you can take it at your own pace and make what you want of the world - follow the spirit guides and play through "proper" or fly/run/swim around and discover things on your own. You can use skills like playing instruments and taking photos, decorate your own or shared spaces, customise your character, chat to people from all over, or just chill in your favourite spot.

I have a co-op buddy too and heaps of good suggestions from others here. Two that I've been enjoying as 2 person co-op:

Wartales: started this after completing BG3 and it was a real interesting change in thinking. This is fantasy party adventure, but you run a team of mercenaries, so it's more about the team build and strategy, rather than the specific character focus that you have in BG3.

The Wild Eight: an isometric survival, crafting, set in a plane crash in the snow. Some story, discovery elements included.

Outward is made to be played by two players. It's a really beautiful survival rpg with difficult combat.

Sea of Thieves.

My recommendation for two people is a Brigantine, just for challenge.

You’ll fight better in a Sloop, but a Brigantine is more fun to operate for two people.

Since you played all Borderlands and just finished a D&D game, why not play "B&B" on Borderlands, there's a game called Tiny Tina's Wonderland which plays like Borderlands but is set in "medieval" fantasy (but still has gun for some reason)

Cat quest 2 if you like cat puns and something casual. (Cat quest 1 is single player and doesn't (really) connect to the storyline of the sequel)

Ark survival evolved is something my husband and I enjoy playing together that's quite fun. The base building and dino taming together is very enjoyable if you're on a private server.

If you give this one a try, make sure whoever is hosting sets their server to private and invites the other person via steam. Otherwise you might get randos.

Serious Sam - almost any version!

Wildermyth is an awesome indie RPG that I've had a lot of fun with as a two-player coop game. It's a turn-based dungeon crawler with a strong focus on role play and party dynamics.

I hear great praise for Across the Obelisk as a coop game from my friends, although I personally bounced off of it. It's a roguelite deck builder like Slay the Spire, but with multi-player, lots of meta progression, and a heftier time commitment for each run.

Gunfire Reborn is a roguelite looter shooter that's a blast in coop. I think it's still in Early Access, but what's already there is enough for me to be happy with it as a full game. To me it's a spiritual successor to Borderlands in combat and gamefeel, but without the grinding.

Unraveled 2 is a beautiful and fun game for 2 people.

Abiotic Factor. It's basically a co-op Half-life.

Diablo 4

Core Keeper comes out of Early Access soon I think and should be up your alley

Has nobody mentioned Barotrauma? Had a few hundred hours of fun with this, my buddy and I. Especially if you don't mind shit being not very shiny. It is unique, and it keeps on giving.

I'd highly recommend Stolen Realms. Pretty cheap too

It's a hex grid turn based game. You can have up to 6 characters (difficulty scales per character) and can each control as many in the party as you want. Turns are taken as enemy, and players with the players able to act at the same time so you aren't waiting too long if you are communicating about what you want to do.

It has multiple "classes" with skill tiers that require you to take a few from that "class" but you can spec however you want.

The roguelike mode is very fun for quick sessions and will reward you with a choice of random skills and armors after every fight, but it also saves if you need to go and play later.

Cult of the Lamb's latest content release is bringing 2-player local coop