Farsight Force power like all force powers is activated with a an action unless specified otherwise. With a duration of 1 round....isn't it more appropriate to be activated with a manoeuvre or as an incidental?

The basic power of Farsight isn't meant to be super-effective in combat. At it's base, it gives you a clear if brief picture of your environment by discounting the effects of darkness/blindness, and is probably of more use outside of combat (where it lasts up to a minute in non-structured play).

You need Duration Upgrades to make this power be effective in combat.