On my file server I ended up growing the RAID (5) and then I went ahead and deleted and remade the partition holding the XFS filesystem. I used Parted to do this.
After parted ran I tried to mount the filesystem but it failed with a bad superblock.
I ran xfs_repair and no such luck, it just skips to the secondary superblock and scans and scans. I'm currently letting gpart run, hopefully it finds something.
Long story short, is there anyway to rebuild the XFS superblock? It was overwritten with a GPT partition table header.
The server is running Arch 64 fully updated. Its a 3TB array of 4 disks in RAID 5.