Rear wheel at edge of dropouts on a Surly Cross Check
When you have a multi-speed setup, the derailleur handles all responsibility of maintaining chain tension. 

The Cross-check frame has the semi-horizontal dropouts so it can be utilized for single speed applications, and it's only for those applications that you control chain tension by wheel spacing.

Where the wheel goes in the dropouts for a multi-speed setup is not super important, so as long as it is completely "in" them, and there is plenty of surface on the dropouts your axel nuts/QR cams ares secured to, you should be fine. Having the wheel nearer the end does make it easier to pull the wheel out without getting too much grease on your hands.