5 mins of rocking = not mixed enough. you literally need to vigorously stir the wort, with a lifting/stirring motion, for 10 minutes to get an even mixture.
when i brewed extract kits, I just used the recipe's OG. unless you screw up the amount of top off water, you cannot miss the OG on an established extract recipe.
dark beer is why i switched to AG and full boils.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10