Just an update, I was able to completely sweep another key last night. There may be other issues with the sweep function though (unless it is simply the batch transaction issue again), but I can only do one key at a time, and I have to restart Armory in-between attempts. For some reason, I have not been able to succeed at sweeping multiple keys in a single go, nor any keys after a successful sweep. Hopefully I can finish up today though, thanks for all the help!
Did you try using the "Multiple Keys" sweep option at the top? It was designed for this
If you don't mind doing one test for us, I just pushed the disablecomments branch to the BitcoinArmory repo. I removed all the logic I think is slowing you down. If our hypothesis is right, this will work. This is the best I can do without getting your watching-only wallet.
P.S. --
I really appreciate you being so patient! Seriously, thanks. Hopefully, as we go back through some other support requests, we'll see that most of them are due to this. Admittedly, I don't do any mining, or have any enormous tx like this in my ledger (and apparently no one on our team, either). Also, this did come up 18 months ago, and I made a huge efficiency fix that was supposed to fix it. But apparently not efficient enough...