If you had enough real games data you could see how often a word is found when present and use that is a weighing factor. Although the arrangement if a word might also impact the likelihood to be found.
Changing the values of tiles will change the game, so you'll have a new mismatch. I think that a simpler fix would be to ban plays of fewer than three or four tiles are placed (I'd say four since three is still too easy). You can still score off the stupid two letter gotchas, but you have to place a three or four letter word down to score anything.
The game would end when all players had two few tiles to play.
