Full analysis
Tabuk does not become a closest-enemy-first targeting RF, despite what her skill may seem like. Instead, she targets the furthest enemy within 5 units, which means she often ends up units who are in between the frontline and backline. Her skill activation shows a visual indicator of this range during battle.
This isn't a particularly useful niche, as there aren't really any notable formations where the most threatening enemies are located in that range.