I think the general Sirlin rule of thumb for balance is: if anything is clearly God tier, maybe nudge it down a bit; everything else: try to bring up to A-tier. That way you're making things more fun rather than taking away what was fun about the other things.
I think in this context the focus has to be on getting cards that never see play to see play, so that more of the choices folks make in the game are meaningful. The Masked Racoon, Rickety Mine, Careless Musketeer, (maybe Scorch), Detonate, BC Musketeer, Jurisdiction, GotG, AConstable, DAlpha, Tinkerer, and Sentry suggestions all fit this bill. I would suggest that the others that need tweaks are the ones in the Red Herring thread.
Personally, the one I haven't seen yet in this thread is Warp Gate Disciple. Has anyone gotten it to work? Can't it be a 1/3 or at least a 1/2? You're effectively delaying your "real" tech coming into play by a full turn to make sure that when it does come, it's the answer you want. That downside seems enough that there should be some chance of keeping it alive for that extra turn.
As for Knight of the Conclave, the real problem seems to be that you wait forever to get it (or work really hard to get it early) and it doesn't do anything but block when it gets there. All that money you spent removing time runes could have been spent just as well just plopping an Iron Man into Elite, with a much more immediate effect.
I think KotC needs to have an Arrive ability. My first suggestion would be "Arrives: Disable a patroller," which would make the opponent think really carefully about how they patrol, and might open them up to some haste plays if they patrol lightly, and would make a surprise early arrival via Time Spiral much more meaningful.
Alternatively, it could be more "Conclavey" and make other stuff work: "Arrives: Add or remove 2 Time runes from a unit (or forecasted unit) with at least one time rune." That way it would have more impact, because it wouldn't just be showing up. It would be showing up with another Knight or with a Mech Token or with an Omegacron or with a Reaver or and making Tricycloid nuts. Forecast's whole deal is delayed gratification. Make it delayed orgasm. You'd still have to time it right with your card draws to make it all work (which is Purple's shtick, right?), and that might be harder than it sounds when you've got no defense because your Tech I play is still in the future.
Oh yeah, let's talk about him! I love the theme with all the 8's, but is there a worse Tech III?
Exhaust, Trash 8 of your workers -> Ready Octavian and disable up to 8 of your opponent's units and/or heroes.
It would make it clear that he's just a big, modified Land Octopus, it would have immediate effect, and if it doesn't win you the game the turn you play him, you're screwed (and therefore might not want to play the ability yet).
I like the suggestions (Midori, Sentry) for clarity a lot, and I see Niko's argument for consistency as well.
I think making cards more flavorful also helps, which is why I love @APALM's suggestion that Vystari be Legendary (even if it means she needs a buff of some sort to compensate). It would also give red some much-needed Mythmaking synergy. Also, it seems weird that she looks like she was influenced by the Tia Dalma/Calypso character. So why doesn't she turn into a water elemental? (Which would be almost identical to taxman?) For that matter, why isn't she blue?
Likewise, @NikoBolas's suggestion that Drill Sergeant automatically gives runes to each new unit, rather than hoarding them and distributing them as he pleases is way more flavorful, and differentiates DS from Blooming Ancient. It would make more of a reason to combo Peace/Growth if you want the combo to go as smoothly as it does now. With that change, Garrison might not need any.
I really like @APALM's and @EricF's suggestions for Troq, but I also think Casta has a point here. I would argue that his stats or levels need a change as well, ideally to make him simple but beefier than others. I mean, Vandy has his same stat progression, but with only 5 levels! And all of her abilities are more useful! I'd consider making him 2/3, 4/3, 6/4, and maybe +1 armor when patrolling (though that's thematically better for Oni), or keeping his stats, but making him midband at Lv. 2.
I see game after game where even when the player's thoughts talk about trying to experiment with some under-used cards, they end up going with a standard line because it's the only real answer to what the opponent has done (which is often just play/kill some units/heroes).
I think ultimately (and I know this is crazy), this is a function of how fast the game is. Yes, it takes a long time to play, but you usually only get to tech in 2x Tech I/Spell cards, 2x Tech II/Spell cards, and either 2 more Tech II or 1 or 2 Tech III. And then feces hits the fan. So while a ton of things are cool and combo well in theory, there just isn't the time/space in a game to get them together to synergize. Anything that doesn't synergize right away, and often anything that is purely defensive, gets left by the wayside.
Now it's possible that those Blue defensive cards might be pretty good if you go all in and push for Gryphons? I think @Shax talked about trying them out at some point? But even if it turns out they make for a viable strategy, isn't there a problem if they're so not fun to play that no one ever wants to?