It's not even the damage that the throwing aspect does, that's fine, it does a shit ton of damage but it makes sense, I mean, you're throwing a fucking lance.
What doesn't make sense is the melee, there should at the very least be a small debuff to the person using it, I mean it turns into a polearm which has no downsides at all, it's super fast and does ridiculous damage in its melee form, it needs a SERIOUS nerf in the melee department. Attack speed needs to be given a massive drop, and so does the damage.
It's supposed to be a weapon for throwing, not for serious melee combat, if I wanted to I'm quite sure I could make do with just the throwing lance as a weapon, not even throwing it, and I'm sure I could get many kills due to how easy it is to use in melee form.