Over the last week or so I started noticing that I when using the deepbit pool my collective Mhash rate was not reflecting the correct total for the number of cards I have in total. There were times when it was as much as 30-40 percent lower than it should have been. I created a different worker for each video card and the problem has resolved itself. This is only my experience but I thought I would post this message in case anyone else may have the same issue.
BK
I actually noticed the same thing when I got set up, but senior members explained that you're just going to see different numbers from time to time on the pool's website because they typically calculate your estimated hash rate over the last 10-15 minutes. The estimate is based on the amount of work your computer requests, which is based on how successful it has been at solving shares, so there's an element of chance involved in the number displayed on the pool's website. Note, this is all secondhand knowledge and your issue may in fact be different since you're using multiple cards, but I just thought I'd let you know so you weren't dismayed if/when you saw a variance in your hash rate again.