Got a chance to run the same build in standalone and you were right, lag was only happening in browser version (which is understandable).
I'll confirm if Duelist keeps dying in standalone when I reach that number of Dancers, but yeah, once you get it going and can clear fights without risk of dying and putting Dragoon traits on everyone, then you can make 10x Dancers that attack twice and a Duelist that attacks twice and gains double stats to reach the cap on the first attack cycle of each fight.