I played Mono-Blue in most of my games and my feeling is that they don’t have answer to hero-based strategies. I mean, Free Speech costs 1 card and just delays the thing…
I’d bet giving Deathtouch to one unit or changing General Hammer, Dreamscape or Jurisdiction for real good anti-hero spells could do the thing.
Or making Law Tech II units affect heroes… Or something with Porkhand Magistrate.
I think that Black starter is really OP too. Most factions don’t have any answer to Thieving Imp for example ! StW should not affect Tech III units too.
IMO each color should have an option to deal with heroes and something to earn card advantage (like Brave Knight, Graveyard or Scribe, before getting an Ultimate Spell).