Here's a co-op action roguelike that's basically a boss rush of high-tier MMO raids

 Rabbit and Steel.
Rabbit and Steel.

The developer of Rabbit and Steel describes it thus: "a co-op action roguelike that recreates the essence of high-level MMO raiding in a randomized, simplified, bunny-sized package."

Honestly, I'm pretty impressed at how true that is. The indie action roguelike released on May 9 and has since racked up 1,545 reviews and 98% of those reviews are positive because, again, it does what it says it's going to do. Up to four players pick a rabbit class, get in line, and get ready to fight bad nasty baddies as you battle up a sequence fights culminating in battles against big enemies that require you to move around a lot.

Move together into a blob. Move a precise distance from each other. Move as far from each other as possible. Move out of a bunch of lines. Move inside a shape, move outside a shape. All the while tossing damage at the bad guy until they explode.

Chill enough to be easily beaten on the simpler difficulties, Rabbit and Steel's high-level battles become almost bullet-hellish if you tip into the failure state of the nastiest enemy attacks. Between fights you get new gear drops, which in true MMO fashion the team can roll on or not.

You can even "accidentally" grief your friends by not supporting them after they take something you want that dropped, in true 100% real World of Warcraft back in 2006 fashion. Though I guess Rabbit and Steel is more like Final Fantasy XIV, since everyone is a rabbit lady.

You can find Rabbit and Steel on Steam for $15, or on sale at $13.50—10% off—until May 16.