I think the price of this doubled since the WoTG expansion because this is actually a good gear for both Campaign (at lvl67 with capped H2H, accuracy isn't a big problem in Campaign) and soloing /dnc, before Kirin's Osode.
It used to be cheap before WoTG because : Scorpion Harness trumps this in xp pt (accuracy+10 much better on IT mobs than Attack+5) ; and no sane-minded MNK would have ever thinked of xp'ing outside of xp pt, because MNK/NIN before 74 is just too bad at soloing even EP mobs. The only use of Arakan was for farming (accuracy being capped on low mobs), leveling NPC, and for looks.
But nowadays MNKs 67+ can xp in Campaign and can solo some DC or SM mobs quite good with /dnc subjob, and I think that's why this gear is now more expensive, since only Kirin's Osode beat this for tanking in Campaign or soloing.
If youre comfortable with your acc (im a hume and i tend to hit everything) you should fork out the cash for these. This is the piece for MNK/DNC for sure.
If you need work on your Guard skill, I'd recommend keeping away from this. But if you're exping/campaigning and you don't need accuracy, this will certainly work