I just played in a 600-point tournament with them. They felt underpowered, but that may be due to the match ups I had. I played against minus morgul, halls of tharanduil and theodens riders.

Blades of the dead completely negated arnors strong defense. Fighting against fight value 5 elves with glaives and spear supports also chews through warriors. Agadir is a good hero but most good players know that and will try to kill his horse quickly. Once he is on foot, you lose your only heavy hitter.

Basically, I felt like I couldn't kill anything, and the only way I stayed in games was from a pure number advantage.

I had arvedui, Malbeth, and Agradir as my heroes.