1. It was very easy to create broken "I Win" Button Combos w/ Artifacts or Obvious Advances
For example, the Orc (unbreakable, etc.) after a handful of sessions was an unstoppable killing machine, which made combat really uninteresting. When another player added the ability to refresh points during combat it was even worse. Then a ton of my prep efforts went into how to make interesting, balanced combats, instead of actually preparing for the game. it was very hard to make challenges that weren't TPK's or cake-walks.
First, every talent, skill, artifact the player have, npc can have. It is up to the GM to create an interesting world to play in. Secondly, about the orc. His talent cost WP to use. He got WP by pushing and getting banes, but that will also damage himself and it is not guarantee that he get WP. An orc fighter typically have bad Wits and Empathy and probably only average Agility. Those attributes can be damaged as well. It is actually very easy to drain an orc from WP. Hardly unstoppable, actually a little to narrow to be a good player character. I don't know what "refresh points during combat" means so I can't comment on that.
I don't give a damn about balancing fights. I add encounters to fit my story. It is up to the players to decide how to deal with the encounters. When it comes to TPK, that is up to the players stupidity. It can happen if the players are really stupid. For me, I think that you rarely die directly in this game and there are far more interesting outcome of a "lost" encounter than TPK.
2. It didn't feel gritty at all
Once players got the talents that let them avoid critical, they were rarely challenged. RAW attribute damage refreshed instantly with a rest. It just didn't make sense to continually artificially create situations that prevented players from resting.
Is there talents to let people avoid critical. I know that there are talents that can change what critical you deal to the enemy and what you get, but that is it and again, players and npc cane use any talent, skill, artifact.
3. Artifacts were OP
I definitely wouldn't allow them in a future game. As soon as the players had that scepter, for example, any social interaction became trivial (like combat above). It didn't make sense to constantly, artificially create situations where someone was coming after the scepter.
Most of the artifacts are good but not extreme. There are some that are really good, like the scepter, but those artifacts come with a cost. Actually more than one cost. First, it has some negative effects that is quite nasty, then if the players use it, that will be very visible and that comes with the second cost, reputation. My players for example used it a lot (the artifact die is good, but I can hardly say makes skill rolls pointless), but they also got reputation for having it. Their life became really miserable. I never had to "artificially create situations" when someone was coming after the scepter. The players was using it, someone saw it and if someone important was nearby (that knows what it is), he might send someone or even himself to go and either get it or try to persuade the players to join his side.