The power weapon cost is to be expected. For one thing, if you give a Power Maul to a Priest and get The Emperor's Strength, that little guy is S5 AP2, or can Smash at S8, making him quite nasty.
And one model who MIGHT do something is a lousy thing to balance the prices for everyone else around. Not that they did, as noted before they just straight up copied and pasted prices from Codex: Space Marines.
Repentia are certainly still a bit dodgy, but improve with Jacobus if he's the Warlord, gaining 5++ which he can make re-rollable.
No, we left Dodgytown two Codices ago. They're unusable for the third in a row. Due to lack of Assault Ramps they'll be open to at least one turn of enemy fire and then still need to get through Overwatch, THEN need to survive being at Initiative one (Act does help there, but there's not going to be many of them left at this point).
The condemnor is being called a meta-breaker. It causes Perils on a unit that it hits, meaning two shots from them kill all the Heralds in a Screamerstar. It also works on models with Psychic Pilot, making for a potential shock for Grey Knight tanks (serves 'em right)
Perils of the Warp only does a single Wound, and if you're fighting an army with a lot of Psykers, that's normally still kinda meh. For an all-comers list, it's far too situational - Psykers aren't anywhere near as bad as mages in WFB to begin with, and all Sisters have Adamantium Will now to make them even easier to tackle.
You can stack Priests in one unit, and get a Conclave for each Priest. You can stick Crusaders at the front and give them a re-roll on their 3++.
... once they're in CC. It's a very important qualification in the current shooty environment. Priests are good for their cost, but there are gradations.
Dominions got a lot better with the option for 4 specials in a 5-strong squad, but their Act is pointless with flamers.
Twin-Linked was great. Ignores Cover is situational, and pretty bad overall. You can toss more Specials in there, which keep them in the game, but you're paying for those. I'd not call it an improvement overall. About balances out.
The Canoness can now get an Eviscerator, a Rosarius, and Eternal Warrior and come in at the same cost as Celestine. That's certainly better than her previous incarnation, though whether S6 AP2 is worth losing the benefits of the Saint is debatable.
If she could have a Jump Pack to get her the mobility she needs to fully use it, it probably would be. As it is, no - though the Command Squad may make it worth it depending on build.
I think Jacobus is the stand-out, though. An extra Act of Faith, Fearless and Counter-attack in a 12" bubble, decent melee if he uses Strength adds up to a lot for not many points. A 20-strong squad with Simulacrum, Jacobus, a Canoness with Litanies of Faith and several Priests is now in death-star territory, which is certainly novel.
It's a death-star once it is IN CLOSE COMBAT. With War Hymns stacking up in the Fight Sub-Phase (which is the ONLY time they work), things look pretty good - but a Battle Cannon shot or two from afar will ruin your day. Admittedly it's a cheap enough death-star that it won't ruin your game (and it will attract fire from other things). Note the Canoness doesn't really have a role in this unit - you can put the Litanies on a Priest.