Taking a closer look, Stuhn - while being a warrior god - introduced the innovation of taking captives. Put another way, he invented the idea of not killing elves. Taking a look at his activities on the other side among elves as "the apologist of Men" he becomes more generally the god of elves and men not killing each other, and by further generalization the god of not killing - i.e., mercy. However, the original two groups of not-killing - elves and men - are relevant. The crux of their conflict was Shor/Lorkhan so Stuhn can be seen most fundamentally as the God of Not Fighting About Shor. Could his brother Tsun, who died fighting about Shor, have been the God of Fighting About Shor?
Trinimac on the other hand was "a warrior spirit of the original Elven tribes that led armies against the Men." He's known for removing Lorkhan's heart and trying to stop an exodus of the only elves that hold Lorkhan in high regard. The most recognizable feature of his sphere is opposing Lorkhan. While it might not seem to make much sense, perhaps it was not so much opposing Lorkhan himself but fomenting conflict around Lorkhan that was Trinimac's sphere. If so, it's not much of a further leap to identify the two lost gods of fighting about Lorkhan with one another.