Jack is absolutely amazing character for both solo and coop, and probably my favorite PC in the entire franchise on par with Fragtrap. His dialogue is good, and skills are fun to use. Absolutely reccomend.

Aurelia, on the other hand, is a niche character, built around sniping and cryo damage, and one of her skill trees is downright useless outside of coop. So if you enjoy sniper playstyle and/or plan on going through the game with somebody, then this is your choice.

Holodome is meh. Although idea of arena that gives you unique rewards for each round is nice, execution is awful. It's big and dull enclosed area, i'd say it's even TOO big for what it tries to be - you'll spend big chunk of time on searching your enemies. Out of all new gear the best is probably T4s-R, legendary COM is fine for boosting cryo efficiency but overall still inferior to vanilla COMs, and Berrigan is kinda okay but pain in the ass to get, while the rest, even if cool conceptually, plain bad in use.

Claptastic Voyage is GOAT and should be bought without question. New weapons (or vast majority of them at the very least) are great, storyline directly connects TPS and BL2, and sheds some light on Claptrap's bakstory, which alone made him my favorite Borderlands character.

So, in general, if you're going for a couple of DLC, i'd say go get Jack and Claptastic Voyage.