Why should a sub attempt be judged the same as a take down? A sub attempt is only an attempt, not a successful submission. That would be like saying you should get credit for a take down attempt because you tried it? Trying to work a submission and not getting it is like a punch that doesn't connect. It really doesn't matter. Also, what would constitute and effective / good attempt? There really isn't a way to gauge it. Now if you want to argue that the guy trying sub attempts is being more active than that's a different argument.
You have to define what a sub attempt is. Shifting your hips and trying to throw your leg over the face of your opponent and failing should not count as a sub attempt in my opinion. Getting both legs around the opponents arm and the opponent trying to stop you from isolating it further should count as an attempted armbar, and, assuming that your opponent did no damage after the takedown, count for more than the takedown itself. Also, you are equating a takedown to a sub attempt when they are different things.
It essentially comes down to, what is closer to finishing the fight/ what causes damage? Takedowns are a means to an end, and should not count for anything in themselves unless they directly cause damage (eg. Randy busting Gonzagas nose). For a round lacking any other scoring, or where the scoring is even, the round should go to the fighter with the most dominant positioning, whether it be on top or pressing against the cage or standing in the center of the ring. Otherwise dominance should mean nothing compared to damage/endangerment.
For example, I remember in the BJ vs Kenny fight Rogan was talking about the pressure Florian was putting on BJ against the cage. What he said was that even if BJ landed just a couple shots, and Florian did nothing but put pressure in the whole round, BJ would win the round. I think this is fair and should apply to takedowns-- that is, worth nothing in themselves but would be part of considering dominant positioning in case of a 'draw'.
Though more subjective, I think really close sub attempts should count more than takedowns. For the reason that failing to stop a takedown does not mean the fight is over, merely that the position is different, whereas failing to stop a sub attempt means the fight is over.
You can also say that the 'level of dominance' is greater in a tight sub attempt,than say from full guard, in lieu of the fact that the defending fighter is confined to a narrower range of options/movements if he is trying to defend the submission.
Like I said, sub attempts are more subjective, which is why I think it is necessary to get more learned MMA people to do the judging.
Personally, I would gauge a sub attempt on how reactive the opposing fighter needs to be to defend it, how long the attempt lasts, and how restricted the opponents is. Of course, only experts would and should be the judges based on the knowledge of positions themselves.