I have two Vintage V4s: one is an older standard black with Rosewood, and the other is the Tony Butler version, like yours. I gig with them often.
They both play very well indeed, no complaints there. The rosewood board one is particularly nice as I've had time to really get the action perfect for me. The pickups on that one also seem stronger - but it could be their height setting. The Tony Butler is getting close, its just a matter of time for me:) And having the time, of course lol.
I've weighed both of mine and they came in at a fraction over 8lbs. That will be including a strap though. So yes, 8lbs sounds about right to me for a bare bass.
As for balance - neither have neck dive, and balance prtty much spot on for me. What strap are you using? A smooth nylon one won't have any friction against your clothes to halt and dive you are experiencing.
Cheers
Geoff