To me, it seems overdone in that pieces it's applied to often don't seem ideal for that format.
To me, bronze sculptures that work well are designed to use the medium and lack of color. A lot of pieces that are normal style that get the bronzed treatment, to me, looks like subpar renditions of the original piece. If the appearance was stronger in the FB format, I wouldn't feel like it's an overdone "fad" sort of thing, but when it seems like almost any piece can get it and often look lesser because of it, then it's an overdone gimmick.
A good example, the bronze Darth Vader statue was made for that purpose and works great in the medium. To me, the Duel of the Fates dio is about the look of the moment from the film. The poses aren't as interesting visually when all you have are the raw figures. Not saying the dio is bad sculpturally, just that the sculpts don't work on a purely scultpural level. It's a combination of the paint applications and the sculpts that make it sing.