Okay sure.
And its true that in a lot of teams/situations, especially once you get to high level, you don't need any Tanking, even for +4's.
Of course there are also a lot of players who think they don't need any tanking, and end up smooshed and ruining the nice no defeat Task Force no-prize. As long as they bring their own wakies though, its NBD.
I don't think it would hurt to improve the Tanker's aggro control some. But its true that its not really going to change much.
I find it interesting though that since a Brute can eclipse the Tanker's role, that simply making it so a Tanker can eclipse the Brute's role is so unpopular.