I recently got myself a Sword Calamity too by accident and back then I only played SC on Vartio's account. I personally find it better than Sword Strike, although a friend of mine still prefers his Sword Strike. Mind you that I only started playing rock (not gimmick rocks like V2A) a month ago(?) after seeing Hexi's Rock tutorial. Maybe its just my bad boost management, but I often find myself running out of boost with Sword Calamity.
Also, I do not KD when I hit with W3 although sometimes I do KD by accident because I'm not so good yet. My nib combo is 2-111-half 3-1-22 (from the back). The Calamity's OS A is a good tradeoff for the lack of Seed Awakening which gives Sword Strike longer boost at 30% HP. The boost down allows me to flee a fellow rock and leave it for my team to gun down.
One more thing that I noticed with Sword Calamity is that you can hit the opponents while standing over their head, which is impossible for some melee weapons. I find it a good ambush attack and some suits (and players) cannot react to that properly. I still haven't customized my Sword Calamity yet, but I originally planned to go C Agi/OC Attack. Maybe a few pixels with speed too, but I haven't leveled anything since my long grind with V2A.
EDIT: I haven't completed a full combo at all. I often flee when the enemy is at 70% HP and leave the rest for my team. I don't know what to do next after landing the first shots.