There are a couple well-known grading/ranking guides you can refer to and join in commenting on:
There are also several discussions about top heroes, e.g.
And there are some recent polls:
And there are even rankings for, um, attractiveness?
And lastly, if you want to ask for personal advice on your heroes, you can create a new post in #gameplay-help-tactics for that.
(@Kerridoc @Rook @Coppersky Recommending this be closed as a duplicate, and discussion continued in an appropriate thread)