To me, there are good mids, around 200-300 Hz, and bad mids, anything 500Hz on up. (Can you tell I LOVE the Ampeg tone stack?) Those pickups have, as you said, 'subwoofery' lows, but no low-mid girth to help define the note and set it in a mix. To try and make up for it, they have an insanely exaggerated top end to put "clack and sizzle" in there in an attempt to help give the instrument a voice. The Les Paul bass sounds good and unique because it has a natural low-mid boom that Fenders and Fender-types usually lack. The Barts completely negate that, and add a crappy sound of their own to boot.
Can you guys tell that I'm beginning to get the Gibson bug? What the hell have you done to me? I've always been a passing fan of a GOOD T-Bird or Les Paul bass, but never really considered them "my thing." The ONLY set neck instruments in my house are my Waterstone 12'er and my wife's Guild Bluesbird. Now I find myself drawn to the "mudbucker side."