You can wear it, but will not get the full benefit of the stats it gives. I have seen a few times that if I wear an item that does not have favor for the Class I am, that the stats even lowered. I.E. It says Defense is 32 more than I have now, but when I put it on Defense only increased by 15, but again like so much in the game it all seem arbitrary. And yes it does degrade faster.
Remember: Some Times the Dragon Wins.