I ended up doing this map with 7 gamers. Recommended is definitely 6-8 guys. We had 2 guys go around taking out the outposts with the drone. Started SW, NW, NE, then went back to the castle.
The 5 guys developed a circle around the castle with 1 guy in the tower. Once the outposts are taken, enemies don't come from that area anymore, so you can focus fire. When the guys come back from capping the outposts, have 1 guy hop onto the mounted MG to take out the helo inbound.
From there, you will get 2 vehicles that you need to destroy. Take them out with either a Grenadier or .50 Cal. After that it's extract. There are only a couple guys there, but there is an ADATS that needs to be taken out for the blackhawk to pick you up.