I had a conversation with their new class Dev about backstab, and abilities more generally, a few months ago because they fully normalize weapon damage for ability calculations. Its a big reason that Backstab feels lame IMO. My suggestion was to use a sliding normalization formula (which I provided an example of) so they could dial it in for specific abilities. The result being that you could make it feel better to use a high damage weapon vs just only focusing on ratio which is how it currently is. This would help backstab feel juicy with a slower mainhand, 2hand weapons could feel better in general etc. Gives you some play with, to use BS as an example, do I keep the high damage primary for fatty backstabs or take this faster better ratio weapon for more white damage. Because there is a adjustable variable you can change it easily for specific abilities as well.
Seems more fun to me but he dismissed it ¯\_(ツ)_/¯
You can somewhat achieve the same effect by just piling on more flat damage bonus but its going to make scaling feel bad. Normalization is boring