Pick up the torque bow or sniper its your choice, I find the sniper best, replace the shotgun and keep your lancer.
When the door opens and you automatically go to the half wall stay there for cover.
Keep shooting Raam in the head and try to get the active reload everytime.
After you run out of bullets for sniper use your lancer to bling fire him and make sure you stay in the light so the kryll wont attack you.
I went through 1.5 magazines w/ lancer and it was an easy kill.