I like the idea of scrappers being able to critically strike. Perhaps my bias for more complex game mechanics will show here, but I think the current passive just seems bland, and impossible to work around because of the inherent nature of RNG. However, I think it'd be interesting to incorporate some sort of mechanic that makes the critical strikes consistent and controllable instead of random. Here's some ideas:
Have a Brute-like fury bar that charges up on attacks. Every X attacks (four or so) is a guaranteed crit, and drains the bar. Possibly also make the first attack in combat crit?
Similar to above, but a Dominator-like power that can be activated as the user chooses to make their next attack critically strike.
A lot more work, but have each powerset from the scrapper pool have a unique, or somewhat unique, criteria that makes attacks critically strike (i.e., Battle Axe crits when, for example, a target reaches 50% health)
I think this would give scrappers a nice change, and given the direction this game has been going since release (with adding more interesting mechanics), I think it would work well. What do you guys think?