This build works on 3 things

Maximizing strengths of the "Sparring Class" weapon: High single-target dps, High puncture.

Minimizing the weaknesses of the "Sparring Class" weapon: low range, meh attack speed.

Maximizing crit chance and crit damage to abuse a "hidden" passive:
Critical hits heal the user by 5% of the damage dealt. Critical hits also grant the Invigorated buff, which increases max health by 5% for 15 seconds and stacks up to 5 times.

with a crit chance over 100% you are guaranteed the buff on every hit.

by going with the average hit "2,566" multiplied by 7.5 = "19,245" the buff heal you 5% of damage dealt so assuming you do the average hit and its a yellow crit you get healed: 965.25
fair enough to say that's absurd.

On top of that with the [Gladiator Might] + Vice secondary buff "20% Critical chance per combo multiplier"
you can get a max critical chance of 525% aka a Tier 5 crit chance.
I cant for the life of me figure out how to calculate orange, red, deep red crits so I'm gonna go ahead and say you get A LOT of health with 525% crit chance and do A LOT of damage.