If by humanoid you mean humanoid intelligence then no I don't consider it plausible, at least not as a result of natural evolution.
While all kinds of parasitical and unusual mating systems have evolved the fact is a human level intellect would counter such parasites too effectively for them to spread and prosper.
Let me set a few presumptions, and explain why I make them, before getting to the main problem.
- If the host species has human level intellect the parasite must as well.
One can hardly use mimicry to prey on your host is you are not intellgent, females are gong to notice a man trying to have sex with them that's incapable of basic language or social interaction. Likewise forced copulation (aka rape) isn't going to be viable, intellect, weapons, and organized group based tactics gives too much of an advantage to have a stupid parasite realistically able to exist and overpower females.
Even more simply humans have a huge number of physical limitations counteracted only by our intellect. A humanoid bodytype only really makes sense in presence of intellect and tools. A non intelligent humanoid would struggle to compete and survive in the wild.
- This species must have had it's intellect prior to becoming parasitic.
Again a non intelligent parasite would not succeed against intelligent humans capable of identifying and actively erradicating a species targeting them. Furthermore one can't really survive with a humanoid body without human intellect.
Thus your parasites would have to be offshots of human, or other homo-x, species
- Clonal parasites would lose due to lack of adaptability
I see parasites coming in two forms. One being a species that basically clones itself and ignores the other species DNA, much like many of the species your listed. This would have the advantage of bein hard to detect, allowing one to use mimickry to hide your clonal nature and spread your DNA.
However sex is super important, clonal species would lack the ability to adapt to their environment. To give one example pre-modern humans suffered significantly from diseases once they moved into larger cities. this clonal species would basically end up being eradicated by disease as soon as they tried to create or move towards a city. For that matter once a disease was known to erradicate them it's likely humans would intentionally spread a disease that was annoying but not life threatening to them - like chickenpox - just to eradicate the parasitic species.*
This lack of adaptability would also mean all of their species would look the same, which eventually would result in humans recognizing other humanoids with this species physical characteristics and shunning them, driving them out so they can't parasite them.*
* note in both of these cases I'm not necessarily saying it's a well thought out complex plan. Society has time and time again evolved counter to regular threats humans faced even without humans fully understanding the importance or even why they were doing the things they were doing. Most people wouldn't know why people with these facial traits were bad or why catching the flu was considered a good thing, and yet despite this cultural adaptations like this can work. In a sense it's a form of cultural evolution, cultures that had the appropriate mechanism to shun or drive out parasites thrived and so passed on their culture creating a unique type of evolutionary adaptation.
- Non-clonal humanoids would be easy to notice as engaging in parasitic behaviors.
Now lets say these parasites engage in sex, and then parasite another species afterwards. This gains them the advantage of sexual adaptation, but it hurts them in terms of mimickry. They would be having sex twice, once to share gamits, and once to parasite another. This makes it easier to detect them since their sexual behaviors are different.
In this case the humans can combat them even easier, notice the ones engaging in whatever mechnisms are necessary to copulate and then parasite someone else, and shun or attack them. This will be done so quickly that the species will be erradicated before it could really establish itself as a species. Plus this sort of sexual parasitism is far less likely to evolve for other reasons...
- boring trump card: parasites don't have time to evolve anyways.
While reproductive parasites have evolved plenty of times they are uncommon relative to other species because the odds of mutations lining up to allow parasitism of this sort are rare, and I'd argue their significantly rarer with mammals since it's harder to parasite a womb then it is an egg.
By comparison the length of time between when the first assorted homo-x species started to develop enough intellect to manage things like speech and tool use and today is no real time at all. Our technology evolved so rapidly that it was barely a blink of an eye from an evolutionary stand point. And that means there frankly isn't enough time for such an unlikely combination of mutations to develop to allow such parasitism to occur before you reach modern day humans.
But wait, there is still an option
All this assumes natural evolution. Guided or manipulated evolution is different. If you throw in genetic engineering, or even some sort of magically driven mutation or adaptation, things are different. You could make a parasitic species in sufficient numbers and with enough culture and intellect to have a chance of parasiting off of humans even if they couldn't evolve naturally.
In this case the species would likely be clonal and lack any kind of genetic diversity (that's far more likely to evolve then a non-clonal species). In the long term this species likely would risk being wiped out by humans due to lack of genetic diversity. But if they only popped up a few hundred or thousand of years ago, well their lack of genetic diversity is unlikely to do them in that rapidly.
So in short, magic made your goblins that prey on women and sure their die out eventually, but that doesn't make them less of a problem to you today!
