i'm not sure that the Mursaat wanted the chosen killed because of saving Tyria.
In game it talks of a Prophecy that fortells the destruction of the Mursaat by the Chosen (and i think they presumed that they would release the titans) so they fixed both avenues by 1)killing the chosen
2)sacrificing the chosen on the bloodstones to keep the titans held
so from this i would say that the Mursaat are simply trying to save their own skins.
the mantle... they don't even know that killing the chosen will save them from titans, and they are simply unwitting pawns of the Mursaat.
Glint is the observer... supposed to stay distant from the proceedings. she simply makes sure that the requirements for her prophecy are met (ie that you go to help the dwarves).
the charr are bad guys, they worship the titans and they are the ultimate bad guys (along with the Lich) without the sceptre the titans would simply trash the entire continent anyway (probably including the charr

). they are not stupid (not that you need to be) you could think of the massive attack by the charr as like a lemming run (with massive axe wielding lemmings)
everyone else is simply pursuing thier own goal to the best of their abilities.
also the Vizier was obviously bad because the Lich says: 'the sceptre will be mine *again* soon enough.'
showing that he had once owned it, and it used to belong to Vizier Khilbron.....