Ugh, looks like it worked, but your blockchain wasn't fully up to date. The 0.4 left is the last three outputs received by that address.
Also, I can see that you did fall into this category I asked about (users don't always know if they are in this category). Each transaction received by that address has tons of outputs. The first one has 1,400 TxOuts of which you are only one.
Armory has a known inefficiency when it comes to transactions that huge, and you have a wallet full of them, so that's as bad as it gets. The good news is most of the processing that's slowing it down turns out to be non-critical (it's for associating address and tx labels with the rows in the ledger), but still important. We might see if we can find a way to disable it on wallets in this category, of if maybe we can just find a more efficient way of doing it.
For now, sweeping should work as long as Armory is fully synchronized. Scanning the blockchain to sweep the addresses should work at "normal" speed, it's just populating the main window ledger that takes forever and Armory trips over itself while it waits.
Ahh, I thought you meant tons of transactions directly to the address, not single transactions to tons of different addresses. I kind of figured this would be a common thing for pooled mining?
So, regarding the blockchain being up to date. The wallet says it fully synced, showing 291259 blocks. The last transaction on that address was block 290240. You're right that the last three didn't get scraped, but that seems kind of weird? I'll try it again and see what happens.