It is not just you have this experience. All ad companies have lots of bot traffic and it is because lots of publishers want to cheat the system and you can issue the refund if you have the proof that they have been sending you that kind of visitors.
There are many adult affiliates that are doing media buying successfully but it is quite hard and it takes time to work it out and I do not really do this and it is not my thing either, so I do not really touch it nowadays.