Wow, that Spartan map was easy. :/
Pro-tip: It's better to damage alot of tough enemies than destroy one.
There's also two good chokepoints at your base to the left and right, use these to funnel the enmeis so you only need two spartas at the gaps. Then you can use your two front-line Spartans to bear most of the attacks, and then attack with the other two after 50%of the enemy is gone. :/
Hope I helped.