Nope it's not worth it for a few reasons. Also, your post is very vague because you never mention which piece of gear you are talking about. It keeps going from one job to another to a different piece of gear.
There's not many mobs in the game that you can "solo" that we don't have easy to obtain gear already to cap evasion. Also, anything you can't cap evasion on, we also have scorpion harness which has a good 10 acc on top of it.
The fast cast isn't that helpful because the recast is only half of the fast cast so in this case it would be 2.5%. You can use Rapparee harness which would give you a 4% recast and be a lot better. This taking in consideration that you are talking about the body piece. Also, for the head piece, the walahra turban would probably be better as well.