Hello,
Without those few low-cost heroes, it will be difficult to make a Gondor horde army. Damrod, Denethor and Beregond are really useful. Mid-level heroes (such as Madril, Cirion) can also do the job, but they're obviously less effective to horde.
Faramir is a bit higher points, but without so much options, he's still a good choice. You can also try captains/kings, who are in the mid-range heroes
But definitely, without the 3 low-points heroes, it is less effective :s
Rohan is difficult to use, because of the cavalry. When you try to make all-cav army, you have low numbers, and you're fragile. I think that relying on warriors only is difficult nowadays, due to their lack of versatility... A good player might be able to use it at his own advantage, I suppose? I've never play an horde army so I can't give the answer :p I'm one of those who like to have "a little of this, a little of that" in an army, such as elites, monsters,... in order to react to multiple threats
And to have a pretext to collect all the minis :pSorry for the bad English :s
