I really like the current direction in relaying attribute information and matching dwarves to roles in Dwarf Therapist. It looks to make it an even more useful (even indispensable) tool. I would like to contribute a few points.
The first few are about presentation. The way I look at it, Dwarf Therapist presents data to inform player decisions, then facilitates the implementation of these. The latter aspect is achieved through a skills-oriented tab, by activating or deactivating individual labours. Now, in the branch splinterz and others have been working on, there is an added roles tab. Most, though not all, of these roles map to a labour just like the skills presented on the standard labour tab. To me it would thus make sense, and enhance the usefulness of the tool, to replace the 'roles' indicator by a duplicate of the first tab, with the same capabilities in terms of directly activating and deactivating labours, just with a different set of data being showcased, whatever you eventually decide it to be. This way you could easily implement your choices, just based on different information. As a bonus, you could optionally present the second data set on either tab through a colour code, like a temperature scale. Say, tab 1 indicates skill and tab 2 a weighted 'fitness' score. Then tab 1 could show the familiar squares and diamonds, but colour-coded on a temperature scale from cold purple to hot red. This would make all the information accessible on both tabs, with a different focus. In the long run you could even have a chooser menu allowing you to customize your tabs to present any two datasets relating to individual dwarves. So your custom tab could, for example, offer two differently weighted fitness functions indicated by square size and colour, respectively.
I've excluded roles that aren't directly tied to labours in this. Those are military functions and those appointed through the nobles screen. You could tack them on at the end of the labours grid, but without the option to activate the jobs. But a separate, special roles tab seems preferable. The selection of relevant information offered would be largely identical to the labour-tied roles.
This takes me to another consideration - what information should one focus on in the first place for any second tab? Here, I think the enhanced Therapist can help with two key questions. Which dwarves are good at a job, and which dwarves have great potential for a job. Which ones can I make good use of right now (and maybe should relieve from other duties like hauling) and which ones could be trained to be the legends of the future? I think it would be great if the two tabs could focus on these individual aspects. My impression is that the former is chiefly a function of skill, whereas the latter largely depends on attributes and maybe traits. So, as a first approximation, having two tabs showcase those properties looks like a good plan to me. That is, I would probably want to disentangle skills from the mix shown on the second one. If my suggestion about colour-coding in the respective other dataset were to be implemented, switching back and forth shouldn't really be necessary anyway to confirm your choices.
Finally, some thoughts on the details of the data. I would generally advocate to try to keep matters simple and do as little as possible to the data as offered up by the game. That is, avoid weighing data, taking means into consideration and so forth. If you do, however, wish to improve things I could think of two very good metrics for the two key features I mentioned above, capability and potential. The first would be the rate at which a dwarf can do a job. The second would be a rate at which a dwarf gains experience whilst doing a job. Both can be measured in-game. As exact attribute and skill values at any one point can also be determined, it should be feasible to work out their exact relationships by relating those properties and then to model them. All it takes is a great measuring exercise. A rather laborious task, mind, but a possible one.
I'll offer a few TLDR takeaways
-replace roles tab with a second labour tab with the same capabilities in terms of assignments, just different data shown
-integrate information shown in tab 2 into tab 1 through colour coding, and vice versa.
-have separate tab for special roles that cannot be assigned as labours.
-create customizable tabs allowing for choice of data source and form of presentation
-have labour tab 1 generally focus on actual capability, tab 2 on potential. I.e. tab 1 skills, tab 2 attributes as a first guess.
-don't convolute, average, apply statistics or w.e. unless it clearly improves the quality of data presented to the user in informing his choices.
-determine the exact relationship of job speed/ rate of experience gain and skills/attributes/traits through measurement. Then make these metrics available in Dwarf Therapist