Very interesting matchup !
What about keeping track of P1 Blackhand Scourge vs P2 Flagstone Dominion where P2 won ? 
I didn’t win many, but let’s contribute with mine !
P1 Vandy rushdown vs P2 Truth tech rush (win with crazy luck)
Some questionable advice from a newbz Blue player
Black starter is incredibly versatile and is your main threat in this matchup !
Deteriorate is of course awesome, but StW is surprisingly even more terrifying. Thieving Imp is not as hard to deal with as it is with Mono-Red or Mono-Green for example, and Graveyard is not as dangerous as it might look like.
Typical P1 Black gameplan is T1 Vandy + Javelineer + Haunt, followed by a hero-based gameplan around Metamorphosis and Dark Pact. Black is quite likely to delay Tech II there.
P2 Blue has many options, and after some games I came up to these conclusions (ok keep critical mind there, I’m not the best Codex player in the world)
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Don’t waste too many gold on cards. Your opponent can heal his heroes by leveling up and remember a Reputable Newsman with a Tower is a higher threat for opponent’s Javelineer than a Brave Knight is. Keep gold to build a Tower (will be useful once Metamorphosis will be on anyway !), Tech buildings and to recruit lvl 1 heroes. (yeah feeding their xp bar is painful but you really need them to keep some cards in hand).
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Don’t go too low on cards. Your strategy implies Tech II and Tech III units, and you need to cycle your deck as fast as possible.
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We all love the Scribe, but yeah don’t forget about Overeager Cadet to build your Tech II as soon as possible. Even if you might not have Tech II cards in hand, Tech II is a threat which might act as a leer to save your Tower.
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Play mostly units. Jail, Manufactured Truth, Eyes of the Chancellor, Boot Camp are awesome as P1 but very dangerous to use as P2. Ultimate spells aren’t your first choice option, use them to react to exceptional board states and with caution.
To sum up, I think that with this on mind you can win something like than 20% of your games as P2 Blue ! 