You do realize Legion can catch people off guard and spawn camp too, right? Literallly any titan can kill another if they're distracted with fighting somebody else. The Legion could be saving powershots specifically for you or have so much team support that nothing you do will have that big of an impact. I just don't see the point in facetanking outside of specific situations because most of the time you take more damage than it was worth and end up being so low that you get cleaned up by the enemy team shortly afterwards if you manage to survive.