Also, sorry Wildlion888, I know you asked, but I need to make that its own post.
Swarmer is a very interesting tower mechanically. Its base damage are very unassuming, dealing a 16 DPS DoT at max that lasts 8 seconds.
However, the tower starts bearing fangs when crowds are involved, both for the swarmer itself, and the zombies.
A Swarmer will inflict its DoT on every zombie that isn't infected by it, with the status being stackable. That means that multiple swarmers will all attack the same zombie, then move on to another one, and so on until the first one is affected no more, in which case they will all attack it again, as long as they can all attack the same zombie at the same time, due to projectile speed mechanics.
Long story short, despite afflicting a status effect, swarmers do not lose damage upon being grouped together, as opposed to Pyromancer.
However, due to its status inflicting mechanics, and the fact it can affect up to 16 zombies due to its 0.5 Firerate and its status lasting 8 seconds, it can be a good powerhouse against crowds of zombies. Notably, every single swarmer's DPS is multiplied by the amount of zombies currently affected by its status effect.
All of that means that, against grouped up zombies, every Swarmer's DPS will be 16 per zombie, which can be 16, leading up to a potential DPS of 256.
Alternatively, you could say that Swarmer shoots for 129 damage (16 DPS * 8s, +1 shot damage), but cannot target zombies it shot for 8 seconds. Honestly, both sound very good.
However, it does extremely poorly early game due to its extremely slow damage build up and the fact it doesn't get hidden detection.
All that being said, I would say Swarmer's domain is MidGame to LateGame, thanks to its insane damage against crowds. However, due to its terrible utility against single zombies, I would argue against using Swarmer as a big damage unit on Fallen King. Because of that part, I would advise against relying heavily on Swarmer, even though it can be a very potent crowd damage tool.
Also, please do me a favor and don't say it's bad just because it has 16 DPS, as you would be looking at it for something it's not made for, exactly like players saying outlaw is bad because it doesn't bypass shields.