Li Shenron
Legend
Moderately armored isn't a terrible feat if your game doesn't have MCing. But if it does, it's a much lower opportunity cost to simply grab armor from a one-level dip.
I think this is the crux of the matter. We have 2 optional modules: feats and multiclassing. They have some overlapping in the fact that both can grant some of the same things (proficiencies).
If you use both systems, I don't see the problem in having two options to get the same benefit, and one of them being cheaper. Just forget about some of the feats and use the rest.
Another matter if you only use one of the modules. We don't use multiclassing (yet) so the only way to pick up more weapon/armor proficiencies is spending a feat. I want all feats to be good, the more balanced the better but I can live with some difference. Weapon/armor proficiencies however break stereotypes, and that's why they are more expensive than their benefits. It wouldn't break the game if Weapon Master granted proficiency in all weapons, but it lessens the importance of choosing a class, an archetype, or a race. Same reason why Magic Initiate grants very little spellcasting.
As a fan of the word "role" in roleplay games, I am fine with this sort of options being expensive. If someone allows multiclassing, it is obvious to me that they already like blurring lines between roles, so just ignore the more expensive options.