Canthans questin in Tyria? Y/N?

yes, you'll still get quest skill reward, but so far from what i can see, for tyria quests, there isn't any skill reward specific for ritualists and assassins. so for those with prophecies campaign, if either your secondary or primary is non-ritualists/assassin, you can save some skill points by completing quests with skill rewards to get warrior, necro, monk, ele, ranger and/or mesmer skills.

Also note you will only get Core & Prophecies skills from those quest's. You will have to use Skill Point's and buy from a Cantha Skill Trainer if you want Faction's only skills.

Best thing rush them to ember light camp than cap elites.