Scrakes enrage after taking damage, which means they can be somewhat easily kited if you avoid shooting them, but they never stop. Both seem to deal similar amounts of damage (except you can circle-strafe Scrakes, which I honestly hope they don't keep in the game, it feels kind of stupid and makes the much less reliable parrying mechanic useless by comparison) and eat similar amounts of bullets (which seems odd, Fleshpounds were much tankier relative to Scrakes in KF1, weren't they?).
I think that the issue with Scrakes is the way their damage and HP combines with the way they rage.
