Use the following missions:
Defend the Sirius Sector Block
Defend the Regulus Sector Block
Defend the Pi Cannis Sector Block
Defend the Psi Velorum Sector Block
Defend the Iota Pavonis Sector Block
Defend the Beta Ursae Sector Block
Defend the Alpha Trianguli Sector Block
Defend the Zeta Andromedea Sector Block
Enter one of the defend missions. Change instances to find the most completed one, EG: 8/9. Once completion hits and the countdown rolls, switch instances, then switch back to the one you just finished really fast. Do this 2 times and you've completed the whole mission! An easy amount of skillpoints for minimal effort. You can continue to get completions all the way till about 5:20 of the countdown. 3/3 with almost no effort.
To make it even worse, Accept the mission back to back, by waiting 30 minutes before completion. This way you can do 2 of the quests in a row in the span of about 5 minutes max.
Please Cryptic, fix this bug immediately.
An idea to correct this would be to limit changing instances to 20 seconds.