The scanning of the blockchain (I've found) was very quick, too about an hour.
May I ask your disk I/O and CPU status? I can't exactly remember which, but, one was very high and the other had quite a noticeable amount of 'background noise' when I was doing it (It was probably the CPU that was very high).
When I loaded Armory it scanned and successfully scanned it. Right after that I imported my watch only wallet and then it had to re-scan which gave me 66 months and did not change its status after about 4 hours. I closed and reopened Armory, and then the percentage went quickly to 99% then it was still scanning and the approximate time left programmed into Armory said 8 minutes, then two minutes later it went up to an hour. Do I have to re-scan the blockchain everytime I import a watch only wallet?