I also have to be honest in that I wonder if you guys play the game much, or play it online like I do, which is a very tough field to play in, as you seem to think trashing and preventing attacks is of little consequence when they actually effect gameplay greatly.
Most of the people here play the game
very much, I assure you. Trashing is important, but only if you can do it fast enough, otherwise your engine won't kick in fast enough. Preventing attacks definitely takes a backseat to launching attacks. You'll notice there are 35 attack cards in Dominion, but only 10 reactions, only half of which can be said to mitigate attacks. Attacking is just so much better than blocking attacks. I agree with the other folks on here in that a lot of these cards seem very weak.
Bomb, as has been pointed out, is just... so... slow. I have to buy Gunpowder, shuffle it in, buy Bomb, shuffle it in, and finally get to trash... one card? I'd have to empty the Bomb pile to get rid of my starting cards, not to mention all the actions I'd use playing them or the other buys I'd be spending on Gunpowder. The one-at-a-time trashers in Dominion, you will notice, aren't really primarily about trashing, it just comes as a nice bonus. Hermit is about something else entirely, Altar is about gaining good $5's, Trade Route gets you some cash, Island nets you VP, Spice Merchant give you some flexibility, and so forth. Bomb needs to trash more than one card, and possibly have the self-trash be optional. You mention how you don't like having your Chapel hanging around once you've got a thin deck, but think about it - would you rather have a single dead Chapel for 10 turns in a thin deck, or have to draw and play 10 Bombs in a deck that's only slowly getting better?
Indeed, the best comparison is Island, although Island sets cards aside and does not trash at all. They both cost the same conceptually, but Island is superior because it also adds 2 VP. I still think Bomb is equally useful, and only falls short of Island cuz of the VP thing.
So... why would I want a Bomb instead of an Island, again? It takes longer to get and doesn't give me a VP bonus. You yourself say Island is superior, and then say Bomb is equally useful.The cards definitely do not "conceptually cost the same", since the Gunpowder cost is severely going to limit when and how many Bombs you can get.
Garrison gives +2 actions or +1 card +1 action.The first is equivalent to Necropolis, a card that's usually a burden. The second is strictly worse than Scheme, which costs the same amount. I don't think the choice is worth the cost.
Sulfur Pit confuses me a little about how the Gunpowder Buy happens immediately. Can I play treasure after playing Sulfur Pit? If so, you're opening a Black Market Pandora's Box.
Soldier seems a bit weak, especially in the face of Musketeers and Grenadiers. The Urchin effect doesn't do a whole lot, and trashing itself to prevent an attack really hurts when it's a Gunpowder-cost card. It's pretty much a no-buy if Musketeer or Grenadiers are on the board.
Reserves might be OK, I can't really decide. The Spy and draw in one turn is nice, and Great Hall is another cantrip with only a weak bonus, so this might be OK at $3.