That's kind of tough call. Heavy bleed loses some of its "heft" in the conversion to perma bleed and I don't have enough experience with class cutter to know how fast she can stack them.
Actually there was some fight modifier that did heavy bleed, and using PW/BHD was fun, because typically it was running several permableeds, several regular bleeds and a heavy bleed. Together they were murdering stuff extra fast.
The problem is 5% threshold. Another fighter with "deal 5% or more to make stuff happen" we have is Claw. The hardest hit she does is with Cat Slide, which for me has about x0.95 damage multiplier (I assume it depends on move level, mine is lvl6).
I checked PW Filia, and her hardest easily accessible hits are sweep with about x0.5 damage multiplier and the final hit of Gregor Samson with about x0.65 damage multiplier. OFC T2 and T3 BBs can do better, but they are probably bad as far as potential bleed sources go.
To do as much damage with a single hit as lvl 50 gold Claw does with the slide, Class Cutter has to have about 10K base ATK, so lvl 40-45 diamond.
Now it depends on what you are fighting. My Claw has circa 8.5K ATK with move bonuses (about +45% ATK), which translates into meter lock up to 160K EHP with Slide. A good defensive fighter has around 80K EHP stock (40K HP, 50% def), 160K EHP would be what? Streak 25? On top of that Claw has access to Fiber Upper which pushes the limit to about streak 30. Of course there are also possible crits and death mark too.
So if you get a lvl 40 Class Cutter with +50% ATK you can guarantee yourself heavy bleeds off a sweep up to about streak 25 and up to about 30 with Gregor which is actually not that awesome.
In practice not all teams have defensive fighters that good, and for me Claw typically works up to streak 40 if you choose your opponents right. But that involves crits and armor break.
TL;DR after doing some math and extrapolating with Claw, Class Cutter doesn't seem to be able to reliably proc her second SA at high streaks unless you invest heavily into ATK and possibly crit. Which makes permableed MA questionable. Again, without heavy investment into ATK.