3 is perhaps more natural to my ear, but I would probably say "I've hardly seen (or met) anyone who says Japanese is easy who is actually good at it." My top choice would be: "I rarely meet anyone who says Japanese is easy and is actually good at it." It is a surprisingly complex sentence to put together, but all three of your versions get the idea across. I hope that is helpful.

I think 3 is best, then 2. 1. seems weird. MET is probably better than SEEN, unless you're specifically talking about some sort of visual experience. Also, (this is my thought, you might want to check on it), in my opinion: HARDLY means never., i.e. you have never met anyone . . . etc. If you just mean that an experience is rare, you need, HARDLY EVER

I think 2 is most natural

This is how I would say it (I've changed the words a bit in an intent to make it easier for me). I have never seen anyone both saying that Japanese is easy and actually also being good at it. Ps. I am not a native speaker.