You have a stable system with good hashrates and zero problems, but the number of shares per card is very low.
10348 shares / 74.75 h = 138.4 shares per hour
138.4 shares per hour / 13 cards = 10.6 shares per hour per card
Normal for 580/570 is 25+ per hour.
You sure you saw those shares per hour for 10000MH difficulty? And not 4500MH or something lower?
Yes, both are correct.
But is not the difficulty the same for everyone at the same pool? Or does it also depend on the power used?
If it is independent then you are in a pool with less difficulty.
Some pools have different ports for different difficulty. Anorak has 3 different difficulties (2b, 4b and 9b)and stratum/ssl for a total of 6 ports.
You use the lower difficulty ports for smaller rigs so less chance of stales, you use the larger difficulty ports to help ease network congestion.