So whilst doing a side missions I came across a specific one where I had to clear 3 areas of enemies. My problem was that the two-handed Plasma rifle was inefficient versus the mechanical foe, my Sword & Shield set fared slightly better but simply could not follow through with damage fast enough to stand toe to toe versus the Chaos unit. 

Would I need a Power Sword that does more damage versus mechanical enemies? Any suggestions? Grenades were insufficient. Thanks.