Here is some knowledge behind it's damage and scaling I tested in SP.

At 310% Melee = 0.1% health per stack

Max stacks =1% health

Dash Slam = 304

Basic attack = 108

if we 2x the Damage it all scales at 100% value.

At 620% Melee = 0.2% per stack

Max Stacks equal= 2%

Basic attack = 608

Note 1: it's flame trail abilitys flat Damage does not scale, it stays at 9 no matter what, however the fire stacks it applys does scale as normal.

Note 2: It's flame boost ability that increases damage will increase every instance of damage output even flat damage from flame trail from 9 to 14 however all fire stacks applied from any source are not boosted