I was going to back a new review but...
Though the new version has not been uploaded by Newgrounds at the time of writing, I disagree strongly with the changes you have announced just there.
I've been playing your game practically every day since it first appeared on Newgrounds, since it's great fun and the cards are excellently balanced, and I don't think you need to tone down lifegain. At all. The problem isn't with lifegain, it's with the fact that Mi-Go Surgery is the worst card in your card set.
The design of the card is excellent (based on the flavor text), but the card itself, compared to the simple and sweet Discreet Doctor, is awful; for 1 more life, you have to pay 1 sanity and lose 2 Arcane. I have only used the card when I'm desperately trying not to lose, and I curse out loud every time I draw it otherwise. I think you may be trying to solve the wrong problem with the lifegain; it's not that lifegain is too strong, it's that Mi-Go Surgery is just a bad card at present. I would even suggest removing it entirely and replacing it with Stake Out, which was a very powerful card even if none of your reviewers knew simple gaming theory back then (information about your opponent's hand = good).
As evidence, here's a comparison of the life gain cards in Necronomicon:
Discreet Doctor - 0 san - Gain 6.
Mi-Go Surgery - 1 San (-2 Arcane) - Gain 7.
Essence of the Soul - 3 San - Gain 14
And the attacks:
Dark Ritual - 10 + Arc
Dark Young Charge - 14 + Arc
Hound of Tindalos - 12 + Arc (ignore Wards)
Rise of the Deep Ones....
etc.
The fact that the better attack cards do 10+ damage each means that lifegain should likely remain as is. Why? Because lifegain doesn't win you the game, it just keeps you alive. Every time you play a lifegain spell, you're not playing to win, you're playing to NOT LOSE. Even then, Mi-Go Surgery is still awful, because it actively makes you not playing to win, more than other life-gain spell, by reducing your Arcane stat. Please think about this, at least for a moment.
Also, the decision to have Dispel not remove Arcane is questionable. Dispel is a powerful effect; this is a fact and you should not be afraid of it, but it's necessary for balance issues. There have been so many games where I've lost a match purely because the computer raced up to double-figures Arcane and I couldn't draw Dispel. Now, it'll be because I can't draw Powder of Ibn-Ghazi, and if I do draw Dispel it'll do squat.
The solution is not to nerf Dispel, but to put the new text on Powder. That way, there are 3 cards that remove arcane: Dispel, Powder and Dawn of the New Day (doppelganger also, albeit situationally). The technique of not overextending your Gain Bonus cards into Dispel is an important one and, whilst it might not be fun being dispelled when you have MIGHTY ARCANE POWERS (tm), that'll teach the player not to spend multiple turns doing nothing whilst the opponent smashes their face in.
The previous rules changes changed the game from a Control perspective to an aggressive one, with Taint becoming cumulative, Megalomania being infinitely nerfed (for the better) and the physical attacks ignoring wards AND invulnerability. I wasn't sure how I felt about that last one; if you're invulnerable, why do you still get hurt by an attack? It's a rules term v. common sense issue, but I can see why it was done; "Oh, you played Elder Sign, I'll use this weaker "Blast 'Em" card to remove your shield, then slap you with Hound of Tindalos.".
Even if you don't take any of these on board, I'd ask you at least to consider two things. One.... Please put Stake Out back in. Stake Out was an amazing card. Two... Challenge 13 has the auto-lose-on-going-insane clause, but City of R'yleh and Yog-Sothoth are both in the card set, making it a luck challenge over skill. Methinks it would be best if you removed those cards from that particular challenge.
Your game is still fantastic and I'm going to keep playing it, but I'd hope that gameplay changing decisions are thought about carefully and not rushed through. Remember: it's your game, make it as good as you can.
