Hrrrmm. It strikes me that different specs have different personalities that affect when and how they should be used.
Peace is extroverted. Heās the kid in the class thatās always raising his hand, or the guy at the party whoās always interrupting to share his opinion. Heās the guy in Pandemic telling everyone else what to do, whether or not they want that.
It seems (from what Iāve seen) really hard to avoid letting Peace just take over a group project and do all the work.
Demonology is a social butterfly. She gets along well with everybody, but is kindof shallow. You expect great depths but almost always see the same old trick. Still, if pushed, she can do some surprising things.
Disease is a hardcore introvert, and also has some social awkwardness. He finds working with other specs draining, and sometimes ends up working at odds with them.
I think Disease works best (though Iām not sure, as I havenāt made it work for myself) when youāre going all-in on comboing with itself. Iām not sure how strong it is against aggro, though Abomination seems potentially very good (esp. against Gliders, or 2x against Crashbarrows).
I also suspect Disease works best as a Rook- or Oni-killer. Those runes can really take the bite out of a hero, and two runes on either of them makes their midbands far less scary. You can probably afford to have them hang around until you draw Spreading Plague.
Likewise, Disease is awesome against Purple starter; Crypt Crawler and Plague Spitter answer Nullcraft nicely, and the runes take Mox out of the picture. They do just as well to make those efficient past and future critters less so.
All that said, for your spec pairing, Iād be trying to pull off Maestro + early fencers + Death and Decay as a pseudo-Earthquake. So Iād be looking for a third spec that can help provide some protection for Orpal while that gets set up. Oni fits the bill with his beefy Readiness and Brave Knights; Rook and Boulder could do the trick, and gives you the alternate Barbarbarian+Two Step strat (though his birds and Quake, being faster and cheaper, and him being easier to keep around, will probably always seem more efficient than poor Orpal). Grave (cheap midband) and Rambasa seems even better, also good Two-Step targets; or you could Tech Lab it for Training Grounds to max Orpal quickly. Similarly, you could go mono-color with Garth and Tech Lab for Resurrector.
Going with an entirely different tactic, Disease+Balance might be fun some time for never-ending Deathtouch. I might go black starter for that one, for Poisonbladeās additional āYou wonāt like it when I touch youā factor.
If you do manage to get it to work, I want to see it in action. Disease is a lot of fun; itās a shame itās so hard to make it shine!