The main reason you don’t see heavy swords anymore is not because it can’t handle carapace, it kills em okay with piety and even good now that you can force it to crit with bleeding bolt pistol, it’s just that the mk15 evis does the same better, with less effort.
Rending should be hardcapped at 50% at most from all sources, but I’d be happier around 30%, armored elites pose little to no threat in this game, for the very reason rending exist.
Having that said, the complete absence of armor penetration from zealot tree does make em the worst choice for CIVII, by quite a big margin. But in the current state where every player can dish out obscene amounts of damage, none of that matters really, even the worst option is more than plenty enough.