The guide to the DBA 2.2 (accurately IMHO) describes light horse as "float like a butterfly, sting like a butterfly">
With combat factors of only 2 v. foot and 2 v. mounted, light horse can't do a lot of damage. All they can do is dance. They lack punch.
And that is only true if you look only at the CF of a single unit. They soon are much better if you use them right, because DBA is a positional game (similar to chess). As any other weak unit they show their true value as soon as they work together with other units.
If they do, enemy LH are a threat to your camp, a nightmare at your flanks, a terror to your rear.
But their right use in gameplay is not easy, needs a lot of experience and good PIP throws...
(As far as I remember the best suggestion to enhance the performance of LH was something like that they use lesser PIPs or none at all.)
Play so that you may be serious. (Anacharsis)
Definitely Badly Addicted to DBA 3.0, HotT 2nd ed. and 2x2 Napoleonics.