Sayne: I'd argue that no matter which path you chose for chapter 2 and 3, saving Triss is the "neutral" choice. You can really throw the Northern Kingdoms into chaos depending on some of the choices you've made throughout the game.
"A pox on both your houses - I'm saving my girl!"
I see what you mean there, but on Iorveth's path this is not so much, as you still find the dagger to free Saskia from the spell, and on sparing her dedicate yourself to freeing her from the curse. It's even possible he goes to do that when you see that last shot of him standing in the mountains looking down at Triss. :)
Triss also mentions Roche is still fighting for the restituition of Temeria, that he survived to reach Loc Muinne and turned down Radovid's bribe.
To me it is the most stable ending, as by saving Triss you also save the conclave, only removing Sile and Phillipa, rather than setting all the kigdoms against mages in general.
But yes, I see what you mean as the neutral path common to both Iorveth and Roche.