after the fight is over you can click the and it will show you who did what. In your video Slayer does the least amount of damage. Watching bulwark since she lasts the longest, it looks to me like wolf(19k), slayer(12k), moon(43k), dman(41k), shaman(19k), and lastly dman,wolf,moon are all hitting simul when it end-battle lags, there's a 43k(moon) and a 41k crit(wolf?) when it resumes.
Bone Dragon *used* to be an easy counter for excessive Start Energy designs. Slayer changed that.