Keep the formulas, we can work those out.
But please let us understand how limb damage works, on the serverside. Not having access to how this works (and there's clearly something weird going on) stops us from being able to explore and figure it out ourselves, even after hundreds of hours of testing.
The main argument for this is that newer classes (and some older ones) have a plethora of limb damage options, with BM being the best example. But even looking at a less complex class like SnB Knight, you have Rend, Slice, Longsword, Broadsword (with 4 levels each), and also Weaponry attacks (warhammer, flails, daggers, throwing knives, handaxes). For people who use "hit counters" (the only real reliable way to play limb classes currently) this means they cannot mix/match their abilities or weapons, as "11 hits" assumes you're using the same weapon the entire fight. It also doesn't allow you to even approximate limb damage on rebounding hits, etc, as 1 of my hits does not == enemy hitting rebounding with a bastard sword.
Would also argue that in today's meta of 6-10 second kill strategies on practically every new or reworked class, a single early or late limb break means a death, which can't be attributed to a "mistake" as much as just dying to the fact that limb damage is unreliable.
Adding on to this, Sawbones is useless. This is evidenced by the fact that it's rare if ever experienced fighters even use it on limb damage classes (its only use case) due to its huge ranges that are often far larger than single attacks, making it useless for determining if a limb is prepped, or to see how many hits are needed to prep or break a limb.
It is clearly not linear as is plain to see if you map out breakpoints. It's also likely that limb HP is not 1:1 with max health, either scaling with its own formula off of Con, bracelet, and level, or it has different formulas for different level ranges or hp ranges, or something.
I'm actually OK with keeping the formulas themselves secret. I like the challenge of figuring it out. The real issue is that it's practically impossible to figure it out when the server is doing black magic on the back-end that as far as I can tell, is completely unintuitive.
It's been mentioned that it could get reworked, but I'd argue that this is 100% unnecessary. We just need to know how it works, currently. If we are allowed to understand the mechanics of it, we will handle the formulas, which will very rapidly be shared with novices and casual players via systems, scripts, or here on forums.
Some half-measures ideas;
Please also consider making Sawbones just work like Assess. Every other Assess-like ability in the game just shows us the actual value, and I suspect the only reason Sawbones doesn't work like this was to intentionally hide some kind of weird back-end logic that doesn't "look good" or something along these lines. At the end of the day though, we don't care - we want (and in some cases, really need) to see it.
Another idea: If you have the Sawbones ability, have a message on limb damage attacks that simply says: "You feel Target's right leg weaken under the blow" indicating that the next hit with the same attack will break the limb. (this isn't a great solution as it doesn't tell you if OTHER attacks would break the limb, but it's better than nothing)