Does that mean that Fend also neuters Frenzy?
It does indeed.
I rate fend and grab fairly highly, though find it difficult to justify putting them on a player early. We may see some of these types of skills start to appear later in this next, longer league. (I hope). THe first league was so short, we only saw a bit of block, Mighty blow and strip ball appear as common.
Fend is particularly good for ball carriers, and cage corners, as Ghostwolf has already stated.