The companion system design principles are not being used in recent Obsidian titles, so it may have been removed.
I looked at the list and I'm not really seeing any areas where PoE and Tyranny deviated.
I don't think he's saying they deviated, only that they're not necessarily designed with these principles in mind.
- Combat/Challenge-viable.
All companions in both PoE and Tyranny are viable if you play it on normal, or even Hard. Then again, so was Myron, he was just worse. If severely weaker counts, Tyranny fails with Barik, and I felt Sagani was useless when I played (don't know in the latest patch).
- Companions should be optional.
Both games did it.
- Next, assuming the players like the companion, the companion should serve as a sounding board for the theme of the game.
Tyranny: I don't think Lantry did much of a good job here.
PoE: I
think it succeeded for the most part, but Kana Rua and Sagani are so forgettable that I'm not sure.
- The companion needs to ego-stroke the player in a variety of ways.
I guess both have this. This is one principle I'm not convinced it's necessary. I think a companion can be interesting without stroking the player's ego and having its own agenda. Not sure if MCA meant it as mandatory, though.
- A visual and vocal/audio hook.
PoE: successful with almost every companion. Edér might be the only one without anything unique about his visual or audio design, but I thought he was still a good companion.
Tyranny: Lantry has no visual or audio hook at all. The other do, but showed how it can backfire. Eb's look and voice only made me hate her even more.
- Foreshadowing.
Durance definitely had it, so did Lantry (in a smaller scale), but I can't remember any other examples. Chris clearly says it's something you
can do, so again, don't know which principles he considers a must.
- Reactivity, not just to player’s actions but to the environment and events taking place.
Both games succeeded.
He does mention 3 more principles in the comments:
companions shouldn't be (1) more powerful than the player, to the point where they can handle the combats by themselves, (2) upstage the player, and (3) seem to have used the ruleset in ways the player cannot to their advantage (ex: they're allowed to have stat allocations that no normal player could have made). All these things can breed resentment.
1 is a problem in Tyranny. Sirin can solo most encounters once she becomes strong enough, as shown here:
2 is not a problem in either game.
3 maybe. Depends on what he'd include in "stat allocations". Pallegina has a unique racial trait and a paladin order the player can't pick, and all companions in Tyranny have unique talent trees.