Several brief points:
1) Note how superior JRRT's Rohirrim tactics are to PJ's movie
(where they just charge in blindly--- and at night!), helped out, of
course by a lack of movie orcish sentries.
2) Given the highly effective strategy of Eomer's lads here, did Denethor later
have a point about how the Rohirrim might have been effective, en masse,
if they'd arrived before Minas Tirith was under siege?. Or would a 6,000+ heavy
cavalry force have been significantly less capable then Eomer's household professsionals? And if so, did Eomer act rashly and unwisely in committing them
against what he must have assumed was merely a raiding force of no great importance, and one that was fleeing Rohan [good grief, was Wormy correct in his critique of Eomer?]