I think fights should be scored on effective offense not defense. If you can stop someones take down you should then counter and use your own offense. This would be the reward for good tdd because if you don't have it your less likely to get your offense off.
If your grappling on the ground and constantly defending submissions should you get points for that? I say no, your not winning the fight your surviving.
When Brock was getting pummeled by Carwin he blocked most of the shots. Should he of won the round? No he was clearly losing but because Shane was to aggressive Brock was able to win, thus rewarding his defense.
If Anderson Silva decided to show off and not throw any offense out and just use his matrix powers to dodge 99 out of 100 strikes should he win? No, he still got hit and didn't do damage.
Lowering the points giving out for take downs especially ones that are just drag downs and lead to nothing would be a good idea though.