I just played through the Sword’s Edge quest line and maxed its challenges. I think it was 19 battles for the quest and another 35 for the challenges (of course), total 54. I got the following traitstones:
Minor Water - 10
Minor Wind - 12
Major Water - 3
Major Wind - 6
Runic Water - 2
Runic Wind - 4
Arcane Blade (Blue/Yellow) - 1
That looks like the drop rate is proportional to their value to me…
This also confirms what has been said in passing: the traitstone drops are 100% tied to the place you fight, so you can set your home kingdom to increase your drop rate of something slightly by defending there all the time. Accordingly, Sword’s Edge is the only kingdom in which you will ever find an Arcane Blade Traitstone.
Oh. And I didn’t know Tau was such a stupid git either. Least empathy out of all quest characters so far!