I would like a group parser because for one (and now I'm going to start calling this my personal running joke) I want to see which player deserves all my Arrows and Balances on AST (lol).
The other is for transparency. There will be cases of harassment with the parser (their already are because some people just don't care about the legality of parsers) and there will be cases where that transparency will help alleviate conflict too.
ie., that one DPS who thinks "they are the best thing since sliced bread" trying to belligerently tell the other DPS how to actually DPS when they have less DPS than the healer. Don't really have a leg to stand on giving (bad) advice about DPS if you can't show you can DPS.
Context is always important and as long as the posters have access to all the information, they can make judgements in their own way. As Reinha / Snoeswys has rightfully pointed out, there is some inaccuracies that cannot be accounted for due to the fact we can vote for multiple options. But a lot of numbers are there for everyone to see for their interpretation and misinterpreting the numbers like what was used in your example will be called out.
This is very true too. Not taking into account the size of the pool of posters he have available, the forum community will be different from the in-game community which will be different pending server to server and these communities will be different from the Reddit community, etc.
Ideally, the best poll to be made is one by S-E in the form of a login census and see what everyone would like. Though they might not recognize to do this if there isn't enough chatter about it on the forum.
Even though the forum is certainly a small and very specific part of the community, it's still a very visual and open tool for the development team. That's one of the reasons I continue to just debate this topic - the exposure it gives to the developers to see if they will move in one direction or the other.