Since the Monquisatdor Explorer knew Hold the Line, I gave him Repel Borders to make it worthwhile when he promoted. He would stop them AND get to attack them all at once, but unforunately, he'll never see the light of Pvp.
The current ranks of Hold the Line are working as intended.
You will see an upgrade at rank 3.
I agree that it is fine as it is. I set Ratbeard's epics at Level 10 to First Strike and Repel Boarders to compliment Hold The Line and now no one can get close to him without incurring at least one attack of opportunity.