[C] Barrier Orb can be combined with [X] Resurrection to ensure your teammates safely revives.
Sage's [C] Barrier Orb is great for denying pushes on defense and for splitting a site on attack. The wall is very fragile before it fortifies, so try to wall in situations where it won't instantly be broken.
[C] Barrier Orb can be used to boost yourself or teammates by casting the ability under yourself or teammate(s).
Sage's [Q] Slow Orb is one of the best combo abilities in the game, especially when paired with damaging abilities like mollies or grenades.