Bishop is without a doubt my favorite (and one of my best) cards in the game. The important thing with Bishop is you just can't... use it as a trasher to build a simple engine (or go BM) and try and buy provinces. You really can't.
The thing with Bishop (like Goons) is you can really ignore victory cards and come out OK. Not many decks can easily get 8 provinces, plus because you're getting points cards like remodel won't help them. Add into this an attack (Preferably rabble, or even bureaucrat) and you almost ALWAYS have a dominant strategy.
Also, depending on what your opponent is doing, the trashing benefit can be a lot less. The obvious example here is Gardens/SR/Duke/etc., but there are many other decks where this is the case. CR is down right now so I have no data, but if your opponent uses Chapel (and doesn't go Golden Deck), your bishop will be very unlikely to help them. Likewise, if they buy a Baron, Counting House, Moneylender, or any number of cards, they won't want to trash out the initial estates and coppers.
Add in great bishop cards like Peddler/Border Village + gainers, and the number of boards is huge.
To answer the question though, YES, bishoping victory cards is good.