I'm sure that doesn't have anything to do with Mortar Volley, of course.
But actually it seemed a bit easier even before that ability is available. Subjective of course-- no hard data. Of course you get that at level 10 so yeah that is a big damage booster.
As AoE goes though I still just love the XS flyby on my gunslinger even if it doesn't do as much damage as other aoe for such a high level ability (level 48).