If your concern is about having larger number of units to play, I understand your point. I personally go for Dunedain because they are a cheaper alternative of units, they may be produced faster, the outpost gives many advantages and they are cool.
About the battalion size, it is not supposed to represent an army size; if it were so, there would be no problem with Imladris, as in 4.5 an army of Imladris may have a maximum of 90-100 elves at best [(1500 cp : 90 cp for each battalion) x 5 + a few banner carriers], which is not a huge amount of Rivendell Elves. The battalion size represents the faction/race as a whole; for example, Lothlorien battalions have 10 units, I personally think that the remaining amount of Dunedain in Middle-Earth during the War of the Ring is closer in number to Imladris elves than to Lothlorien elves.