I think that the "line-of-sight" modifier is applied to javelins as well, though I must admit my memory is a bit clouded here. Basically, you want 2 ranks on flat and 3 on high ground to maximize volley potential.
Personally, I find javelin results very random, just like naphtas. They are situational and you can't depend on them too much. But in early they are pretty much the only armour-busting unit, and they do come cheap.
/KotR
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