I very much prefer letter grades, A B C D F, and if we wanted to be cool, pluses and minuses. (But this would just make it the same as the 1-10 scale-- D and F really don't need +/- and A+ is unneeded too, unless it's ebay.
)
However, in reality, this doesn't really matter, since "average" tends to be viewed as mediocre, and thus most episodes simply aren't going to have an average rating of 6 unless you have a bunch of masochists following it.
In fact, you'd be hard pressed to find any poll that averages towards that. Though this is because discerning a 4 from a 2 is well... not needed. You weren't happy anyways.
The other thing is I'd expect most people to ignore the descriptors and insert whatever the hell they want. Which is fine really. I don't follow it either. In fact, none of my episode ratings from different series are consistent-- I have a different mindset when watching different kinds of shows.