If you’ve got the season pass, it’s worth it to pop into the multiplayer for a bit, even if you just want to try out The Harvester.
Unto the Evil is a bit expensive, but offers some pretty good additional content for the multiplayer component of DOOM. If you're a fan of that, Unto the Evil is required to keep pace with the community, but otherwise it may be best to save your efforts for the next DLC which should cater to the more popular campaign mode.
In summary, Doom Unto The Evil is a fun DLC for the main game which gives players some enjoyable new maps, a couple of new weapons although the handgun really shouldn’t count and of course the Kinetic Mine and the new playable demon which adds to overall Doom mythology well.
Many expansion packs can easily be dismissed as “more of the same for those that want it.” Unto the Evil sidesteps this. It’s an easy recommendation to players that liked everything about the speed and feel of the combat but disliked the maps; these new ones are so much more enjoyable.
Doom: Unto the Evil is an… okay DLC, with nothing really special to say about it. The things it offers are fine and all, but with a somewhat ridiculous price tag attached to it, especially since almost everything included feels more like mods than material created by a team of professionals.
The answer to whether or not the Unto the Evil DLC is worth it depends on what you're looking for. If you're in it for the new maps, then you're better off waiting for the private match option since it can take a long time to see them under normal circumstances. If you want it for the customization, then the DLC has lots of satisfying options. If you want the weapons, then you'll be fine since both the Kinetic Mine and Harvester are great additions, while the pistol is only there if you want things to be tougher. At $15, the DLC is pretty expensive by itself, but if you want to add to the multiplayer experience, this isn't a bad pack.