That's the big detriment to the evil path, none of them actually realise they've got a tadpole sitting on their brain that could turn them into a illithid at anytime. There's also pretty good indications that they're all being manipulated to varying degrees by the tadpoles and whatever is controlling them. Your character's tadpole is different because someone or something tampered with it but on that we have no idea why and there's no indications that the cult's master(s) are behind it. Even for an evil character, except for the psychotic, your best bet is to aid the grove and rescue Halsin. Now you don't have to help the Tieflings but getting to Halsin is presented as your best option with all others getting progressively worse.
On the subject of other tadpole options, last time I played there was no option to argue with the hag after
You gave up your eye, but the hag failed on her part of the deal to remove the tadpole. I feel like there should have been a dialogue option to demand your eye back, or at least demand something else from the hag..?
Has anyone seen an option like this in more recent patches, or is there still no other option besides accepting the shit deal and/or getting revenge?
I don't count the deal she tries to make when you've almost killed her to count; that's her bargaining for her life and separate from this first deal.
If you didn't play after patch 4 then, sorry, your feedback on the plot is a bit outdated. They patched the plot as well in patch 4, it even was in the patch notes. I can't say how much, I just checked on the start and some mechanics after the patch, but I can tell you that for example the conversation with Nettie after patch 4 has nearly nothing in common with it before the patch.
I recognize that my feedback is a bit outdated. That said, I haven't seen anyone post that the evil path has been fixed whereas I have heard people talk about the Nettie/general Grove changes many times. If someone can tell me otherwise, great!
I also see nothing in the patch notes mentioning the evil/cult route. I do see the "Added reactivity for Druids" section.
