I just gave up on a run using the atgeir as my main at least partially because of the mechanics. I don't know if it's a bug or intended, but the primary attack is not very good IMO.

I've never had an issue with sea serpent meat, so I don't know what would cause that.

As for deathsquitos, 9 time out of 10 in a permadeath run my death because of deathsquitos. You just have to be able to withstand a couple of hits (at least) from them. I have never experienced them just appearing around me, though, and I don't think they should be nerfed. They are one of the few aggressive mobs in the game that make the game fun.

Can you post links to clips that show them spawning near a player? I don't think that's supposed to happen.