Yeah, while this wasn't true at Heavensward's release, Paladins and Dark Knights no longer share a stance. Grit is rightfully weaker than Shield Oath, since Grit is -20% damage to Shield Oath's -15%. This really has made every Job but Bard and Machinist have different stances mechanically.
This was true back in 2.0 as well, just look at Scholar and Paladin's leveling list. And why, after Ninja was released, they didn't give Arcanist an actual heal worth having on a damage dealer, like Second Wind, and made Physick into something Scholar got at 30. Just crazy that we haven't gotten some revisions by this point.
This is a bit of an interesting thought. Similarity while it can be useful for balancing, also isn't in my experience, the best option, especially in games that will eventually have who knows how many. FFXI ended with 22, FFXIV could reach or eclipse that number, or not. In cases like this, its often better to actually make classes radically different for identifiable mechanics, like how Machinist has pseudo-combos, how Monk can mix and match their combos, and Dragoon's randomized fourth combo. Likewise, it's important to make classes have different things they bring to the party, you can't compare Rage of Halone to Delirium for example, they both have greatly differing effects and uses, incomparable effects and abilities like these are healthy for a game, because the more you have, the more combinations you can make to find balance for even the weakest Jobs mathematically.