Guild Wars: Is It Wise to have a Superior Marksmanship with a Barrage build, or should stick with minor?

Using a Superior Marksmanship rune for a Barrage build, would be wise. It is a general rule of thumb to put the most attribute points in the skill that is doing the most damage or giving you the most benefit. Of course if that is the only Maksmanship skill that you are bringing in your build.

Although many players love the spell, you have to consider when to use it. In some areas it can be very good to cast unyielding (UW, FoW), while in others (quest areas, not missions - where res by portal is possible too) other forms of resurrect like restore life and rebirth are the better choice.

If you are a monk, you had better to take Word of Healing (elite) instead when not in an area that makes Unyielding Aura very useful. If you know the entire team, bring Word instead. Monks usually heal, and when a monk reseeds he doesn't heal. A teammate that doesn't play a monk to res teammates is good. With good fast casting are so good at this they are affectionally called rezmers.

You won't need a build. All there is too it is having a Mesmer with fast casting (a lot of mesmers already use it, as it is their primary attribute), who has his normal skills (no matter if it's illusion, domination or inspiration) and a res spell. With high enough fast casting, the Mesmer can effectively half the casting time, making it faster and harder to interrupt. It also helps because the monk can continue healing, and mesmers have such good energy management available to them the energy should not be a problem to them.