So yeah, I'm pretty confident that the array isn't hosed. (at least I'm telling myself that.) The drives are healthy, but mdadm sees two drives as spare but they should be part of the four disk array.
I made some progress since OP; I was able to run:
mdadm --create /dev/md1 --assume-clean --level=5 --verbose --raid-devices=4 /dev/sda2 /dev/sdb2 /dev/sdc2 /dev/sdd2
Then, all drives appeared healthy and in sync. (all Event IDs are/were the same). Next problem came with trying to mount. I wasn't sure of the file system, but it appeared to be xfs by comparing to the other NAS box. I had to edit mtab to get the mounts set because mount first complained that it wasn't set in the config. (which is weird, as I thought a manual mount should work, too.)
The mount failed, and the logs stated:
XFS: bad magic number
XFS: SB validate failed
So at this point, I'm running xfs_repair -n per this post: http://hardforum.com/showthread.php?t=1476237
This guy's scan ran a few hours... but found a candidate SB for secondary, then re-running xfs_repair without the -n switch fixed it for him. I'm crossing fingers here.
I didn't know a lick of this Linux stuff before today... took me too many google searches just to figure out how to use vi to f'n insert text! I don't know how you guys do it!