Pawniard evolves at 52. The only Pokemon that evolves at a later level than Larvesta is Zweilous (64). I remember reading an interview in which the creators explained that they wanted to make the Unova Pokemon evolve and learn moves at later levels in order for the player to have something to aim at, even when they are at a high level. I never played Platinum (only had Pearl), and BW2 doesn't have a moss rock available until the post-game. XY was my first chance to play with Leafeon, and the problem has been solved. Gaining exp points is easier than ever now, and level 45 is not that high really, Razor Leaf is usable until that time. Compared to gym leaders, Leafeon learns Leaf Blade when your Pokemon are around the same level as Olympia's (Anistar City). That's the 7th Gym, and I think that is very reasonable. Fortunately these levels Pokemon learn moves are flexible, so they were able to fix Platinum and BW's mistake with Leafeon in BW2 and XY/ORAS. But all of those Pokemon that evolve way too late to be usable when caught in their first stage, there is no redeem in sight. Not just Larvesta, that's just the example I pointed out because out of all first stage Pokemon it evolves the latest. But like you said, Pawniard, Rufflet, Vullaby, Mienfoo, Noibat, Skrelp, ... they're sort of doomed in that regard. Shauntal's Pokemon, for example, are around level 48. This means that the Pokemon I just noted will not have evolved when battling the Elite Four at their own level (though Noibat and Skrelp did not exist back then).