I don’t see a lot of mentions for Javelins. After playing with them for a bit, I have found them to be pretty awesome, so I would add them to my favorite secondary weapon, for almost all my mercs except for pure archers.
At first glance, they might seem ineffective, especially for melee trained mercs — but I noticed even with a low hit-chance tooltip, they still connect at reliable frequency, granted they usually hit shields on shielded opponents. So I have often found use for them during the gap-closing, when I can either get adjacent to the enemy, and then do nothing until the next turn, or get close but not adjacent, and then throw a javelin in his face (and surprisingly connect frequently enough), and then let him close the gap next turn, forfeiting his extra attack, while I switch to my primary weapon and unload a full round of attacks.
Another HUGE benefit to javelins is I get to keep my shields up! Unlike switching to billhooks or other ranged weapons, which would normally be a bad idea for the front-line shock troops, with javelins I get to keep my defensive line defensive, while simultaneously presenting an offensive hail of damage at short-medium range.
I haven’t used them as a primary weapon, although I can see a “skirmisher” ranged support build as potentially viable with javelins.