There is no solution to fix the way spears and thrust works, the animation just sucks. Devs will not fix the animation, or substitute it, they don't have the balls to change a core part of their game, maybe they don't even have people with skills to do it. It is not that complicated either, just buy or rent a good motion capture suit and hire someone with proper skill to do the movement(s). This would be by far the easiest and cheapest way to fix this, but they won't fix anything, at this stage they just want to finish the game and not make any bold moves.