I think everyone understands the versatility of chain of vapor.  All of the scenarios are fine as long as your opponent only has 1 hate card but you win those games anyways.  The problem is when someone puts a jailer into play and then tinkers for Platinum Angel.  Gaddock Teeg + Tormod's Crypt + Pithing needle.  You have to think a little more closely about your countermeasures when you expect to need chain of vapor to deal with leyline.  I wrote out the list so people can make an informed decision, not so I can get called paranoid or lectured about chain of vapor, a card that everyone has  a million of.

You also might reconsider 4 ancient grudge.  Its very hard to cast that card under a thorn of amethyst.  You might want at least some ingot chewers. 
-J-

I haven't tested Gargadon, but I suspect that it would be hard to implement in practice.  Most decks are perfectly capable of killing you in a couple of turns if left unmolested with hate pieces locking you down.  It is hard to imagine gargadon being relevant in time.  Not to mention you have quite a few cards that will never be perms (serum powder, unmask) and though you may have the same number of lands as the legacy version, bazaar doesn't cast narcomoeba or golgari thug the way that the legacy lands do. 

Firestorm doesn't really compete with darkblast (or at least it probably shouldn't).  It competes with the contagion slot in the sideboard. 
That spot can be taken by a couple of cards, all intended to deal with the following problems: Yixlid Jailer, Gaddock Teeg, Magus of the Moon, Platinum Angel, other various and sundry creatures that affect the game without combat (peacekeeper, glowrider, samurai of the pale curtain, etc.)

Contagion, Sickening shoal, slaughter pact, firestorm are the candidates (I suppose you can look at darkblast too then)

Contagion:
Can be cast for free
Is a black card (can be pitched to Unmask and other contagions)
Can deal with 2 yixlid jailers

Cannot deal with Platinum Angel
Cannot deal with Gaddock Teeg
Requires a 2nd black card to be useful

Sickening Shoal:
Can be cast for free
Is a black card (can be pitched to Unmask and other sickening shoals)
Can deal with Platinum Angel
Gets around indestructibilty (rarely, if ever useful)

Cannot deal with Gaddock Teeg
Requires specific black cards to deal with certain threats (cabal therapy + Sickening shoal =/= dead Teeg)
Can only deal with 1 yixlid jailer

Slaughter Pact:
Can be cast for free
Is a black card (ibid)
Can deal with platinum angel

Cannot kill yixlid jailer (deal breaker)
"Lose the game"

Darkblast
Reusable
"Dredge"

Can't deal with multiple yixlid jailers
Requires an entire turn and 2 lands to set up killing x/2s
Incapable of killing x/3s by itself


Firestorm:

Can deal with multiple yixlid jailers (or other creatures)
Can deal with creatures of varying size and shape
Discard outlet
Can dome

Cannot be cast for free (matters in situations where you need to deal with more than one hate card)
Is not a black card
Must have X targets
Must have X cards in hand
Can't target Sphinx of the Steel Wind


I played firestorm the last time I played dredge and it was ok although I only cast it once.  The other 73 cards didn't cooperate as well (1 cabal therapy cast in 7 games) but firestorm was ok.   I think I would be happy with whatever I sleeved up on the day.  The day you have Firestorm you'll need it for unmask and the day you have contagion someone will put Platinum Angel into play against you.  Just how life works sometimes (or maybe that's just me).

-J-

Isn't Cloister strictly better?  Both cards cause you to have 0 cards in hand on your opponents turn and both cards let you draw 2 a turn.  Assuming you don't want to cast One With Nothing isn't it just better?

If your only requirement is dealing with Inkwell Leviathan then Thornweald Archer may work.  It has deathtouch and reach.  Not good against DSC, Akroma or Progenitus but good against Hellkite Overlord and Inkwell Leviathan.  Also you can clamp him away for +1 if you really need it.

Strategic Planning?  It's P3K and therefore super expensive but it works. 
Impulse and Peer Through Depths also dig pretty deep. 

Glad I could help in more ways than just letting Tezzeret players practice Vault-Keying me on turn 1...or turn 2 with Force of Will Backup.

The worst cards are basically leyline combined with something like extirpate.   Everything else is easily therapy-able.  Sticking to the constraints there are some annoying cards like Samurai of the Pale Curtain (shuts off Ichorids and Bridges but not dredge), Gaddock Teeg (shuts off Dread Return, Contagion), Glowrider (makes is difficult to cast spells in the manaless version).  You need to have: More than 1 hate card, more than 1 type of hate card, and some pressure.  Most people will have Chain of Vapor so if you don't double down on hate, you'll just get it Therapied or unmasked away when they can cast chain.  You could just give the matchup away if you think you can't satisfy those 3 conditions.  There are a lot of sideboard spots available if you do that.  It is not a recommendation but I am raising the possibility.  Most every game I lost all weekend (and they numbered many) consisted of my opponent having at least 3 different sideboard cards.  I won't keep many hands that can't deal with 1 hate card; most hands can squirm through 2 if there's not enough pressure but 3 is a bit ridiculous.

My name's Jay Carter and I live in Eastern NC.  I'm a huge soccer fan and I fund my hobbies by being an engineer for the Navy (civilian though so I can't be shipped off to crazy places without wanting to go).  I am a constructed aficionado and spend most of my Magic playing time with Standard and whatever is in season for Qs.  I have only recently started playing Vintage semi-seriously and am still toying with the idea of acquiring cards specific to the format.  More tournaments within 6 or so hours would probably be the push I need.  Seems like a neat format and I'm looking forward to getting further into it.