We are having an argument on Discord and I need the people to weigh on on this issue, because I will not stand for this slander any longer.
I think it really depends on the Pokémon and your match up. For instance, if you're running a defensive Pokémon or facing a Pokémon that uses a higher critical hit chance moves it is pretty good. Otherwise, it's okay.
As someone that runs a lot of nuzlockes: I like these abilities. I am not at the point of running lucky chant though.
As a nuzlocker, yes these are good abilities. Being immune to crits takes away one of the most common factors for deaths in my case. I cannot count the amount of times I've lost a mon to a crit at this point so if I have a mon with shell armor/battle armor that just means I don't have to worry about RNG killing it then if it dies is more often than not my own fault for it dying.
I think they're good abilities, especially for blocking Urshifu's busted guaranteed critical-hit moves or other critical-hit shenanigans, but the issue is that many of the Pokémon with these abilities have more useful abilities (Falinks has Defiant, Kabutops has Swift Swim, Drapion has Sniper, etc.)