I'm not sure what is trollbait and what isn't, but my main has been off and on throwing throughout the course of my play, and here's my opinion on throwing lances (I'm going to echo on a lot of points already said).
The context of my current gen is 21/18, 7 PT 7PS 6WM 6ATH 142 throwing wpf 84 pole wpf @ level 31. I use 2 stacks of jarids, 2 stacks of throwing lances for my weapons. My normal behavior is to save 1 lance for melee until I can scavenge a better polearm.
1.) It's actually just worse than a short spear on the melee stats @ base level (2 less blunt on swings, same pierce iirc -- dunno tired). It's very similar, and behaves the same way (annoying stun on the sideswing, and a pretty decent stab). It does cost 5 times the amount, but you're paying for the ability to throw it and go for great lols. Personally I think its melee stats are fine. They are good enough to justify being used in melee, but against anyone who has a clue and a decent weapon, it's likely the other guy will win.
2.) The only people these are 1 shotting are cav (mostly from the speed bonus) and people in under 40 armor. Even then it's possible to live. I routinely get hit by a throwing lance and live with 41 body and 30 leg armor. I also have 0IF. That being said, it usually consumes 60-100% of my hp.
3.) Horse throwing is maximum troll build, but little effect from what I've seen and tried. I don't think you can make this build truly dangerous unless you are over level 30. You have to be too close to be effective, and at that range why not just lance or 2h for maximum kdr play.
4.) I like the idea of changing the throwing lance to a 2 slot 3 stack item. With this change I think they would need a stat change. Perhaps a lowering of the damage coupled with an increase in accuracy would make sense. The idea being these are the arbalest of the throwing weapons, designed to disable/pick off very high value targets. Not designed to throw at peasants.
All in all, I think they're pretty good. I would be fine if they don't get touched at all honesty, but I did like the ammo count + slot increase.