As another trader on this site said to me this morning - I'm just happy to trade cards I don't want for cards I want -- which is a good way to look at it. Are you more interested in having the Guerrero and Witt than the Mountcastle?
It is an interesting trade. You can look at it from many different angles. If I was collecting Vlad and Witt and needed those cards, I would do it. If I didn't care about those guys, I wouldn't.
If you are in the middle on those guys, maybe just see if another card of a player or set you really like (even if it's like a $1 card) can be thrown in, just to help you feel better about the trade. I suspect different people will have different opinions. In the end, it is really a personal decision as to what you want to have.