i personally can't see a big use of valhala gear (well maybe with double march i guess) but i'm not fan of the slow
Guess could be used for JA if you don't have hydra haubert. but meh
-Magic damage if you lack aegis. The body is a top /rdm body and blood-tanking body too, since all the spells have such low timers. The head is mostly useless except for looks, but I toss mine on when I tank stuff just for the look since most HNMs are so easy anyway to co-tank.
Sure it adds 2 seconds to all my recasts, but it adds -tons- of epeen to rub in the faces of the other NA shells watching the fight, since my shell has 6 of them, and no other NA shells have any, and only 1 JP shell has 2.
FFXI is just a big fashion show after all. Most of the time, epeen and looks > usability.