The best way to defeat General Raam on Insane is to go with co-op. You have twice the smart firepower allowing one person get the Torque Bow and the other the sniper rifle.

The bow carrying player should have at least ten arrows. The Torque Bow is the only weapon other than the grenades that will hurt the boss seriously when he has his Kryll shield. The explosion of the tips will also send the Kryll flying, allowing your partner to get in a nice head shot with the sniper rifle for a good one-two combo.