I've meant to go through this for while, but it seems a big task to go through all the cards, so I'll just comment bit by bit, in the order from the starting post. Note that I haven't read previous comments, so there may be things in here that have been discussed before.
Jane Doe - "trash a card from your hand" is by far the most useful option on this, the rest is very situational. I would try to reduce the number of options. +1 buy seems superfluous on a card that you'll mostly get if you already have extra buys. Gaining a Horse also hardly ever seems worth getting this for. The when-trash seems a bit out of place on this card; it makes more sense on a card that isn't already a 1-shot.
Healer - the Reaction is clever in that it decently counters both discard and junking attacks. I feel like the on-play effect is too strong though. Compare Trade Route, which costs more, is weaker, and does not have a Reaction. Not sure what the best fix would be. I think removing the trash on play and, to make up for it, allowing Healer to also trigger upon other healers being played would be a decently interesting nerf.
Mirror - this is a neat card. I worry that it can get a bit confusing at times - as written, if I Mirror a Mirror, then I only need to trash one Mirror and no other card.. is that intentional? It might be better to use a wording that requires a card trash, like "you may trash the played card. If you didn't, trash this."
Monk - seems fine. One worry is it might be too strong with emulators; maybe make the +VP conditional on having Exiled the Monk (Way of the Mouse/Monk is crazy). There are also ways to make this go inifinite, if you have a way of continually gaining Monks (e.g. from the trash) to discard your Exiled Monks, but that seems like more of a feature than a bug.
Resistance - this one has a bit too much going on for my liking. I don't see why it has the thing where you can put it back on the mat instantly, I think that should just be scrapped. I am not in love with the double dividing line, but I can kind of see why it has extra buys. It might be a solution to just put the buy as an extra on-play effect and get rid of the when-gain.
5 at a times seems good, yes? I'll be back
Don't go posting new cards that mess up my order in the mean time!