Devil's Advocate: Bury the Blade can be plenty amazing against Standard characters too if they have really high damage saves, good armor, or the Toughness quality. A good crippled limb can really take the fight out of a tough Standard enemy (who isn't always a mook! You can build some REALLY tough "standard" enemies if you have a mind too!)
It is true that you can easily end up specialized for Special vs Standard, but I don't really think the weapon chains inherently have issues like that. My Assassin is ultra good against specials and our Martial Artist is ultra good against standards, but that's just because of the numbers game and our choice in magical items and class features.