That depends on how you want your mass battles to play. There's no facing in LR, no flanks, rear, etc. Usually in mass battle games there's an element of trying to get these things. There's also no rules for multiple combat, so you would not be able to orchestrate that kind of thing either. It is more warband style in my eyes.
That's all true. I think, though, that the abstraction of LR/DR combat (i.e. its reduction to "clashes") is preferable to the Warhammer style in which five or ten or twenty men wheel and otherwise move in strict formation.
I think in fantasy games in particular, a looser approach to combat (think "hordes"!) can work quite well. And while there are no rules for multiple combat, the effect can be created by having a unit to the rear of a retreating one, or ready to charge into the flank of a battered one.
As a comparison, Hordes of the Things has plenty of focus on the importance of flanking and the like. It's usually played with fewer figures per side than LR/DR (around 36, as I recall - I may be wrong!). While I remember enjoying it (it's been a while!), I certainly prefer LR/DR. And I'm not convinced that seeing an LR unit as 120 men rather than 12 makes the game any worse.
A thought experiment: could you play a good simulation of the Battle of the Five Armies from The Hobbit with DR (counting one man as lots)? I think you could.
On the orcish side, you'd have the bodyguard of Bolg ("huge goblins with scimitars of steel" = foot men-at-arms, 6 points), two units of wolves and wolfriders (mounted yeomen, for 8 points), three units of smaller orcs (serfs, for 3 points), a unit of larger orcs (foot yeomen with mixed weapons, for 5 points, and a unit of bats (bidowers, perhaps, for 2 points).
Then on the other side, you'd have Beorn (foot men-at-arms in one for 6 points), Dain's dwarves (expert foot sergeants for 5 points), Thranduil's Elves (expert archers, 5 points), the Men of Dale (foot sergeants for 4 points) and Thorin's company (fierce foot at full strength but with just a handful models for 4 points; the "fierce foot" designation is to simulate their small number but heroic ferocity).
Would that give you a decent battle that might play out something like the book? I think it might.
Of course, this all accords with what you say about how you want your battles to play out!