Johnny Novgorod said:
It's a TF2 knock-off. What else is there to talk about, if not skins and their design?
Tracer = Scout
Reinhardt = Heavy
Torbjorn = Engineer
Widowmaker = Sniper
Mercy = Medic
etc.
Filling a similar role as is not the same as them being equal to each other.
Tracer and Scout are both speed based chars, but it looks like the way that they actually play will be very different. Scout is (usually)about jumping, correct use of buffs/debuffs, and getting behind an enemy for a point blank shotgun kill. Tracer seems more horizontal and chip damage based, and the 3 second rewind ability looks like it'll be the move that separates the skilled players from the newbies.
Reinhardt and Heavy don't look like they play similarly at all. Seriously. Reinhardt uses his shield and charge abilities to close for powerful melee hits, Heavy is a medium range mobile turret. If anything, Bastion seems like he'll be playing a lot more like Heavy than Reinhardt will, with the turret mode and self-repair abilities.
Torbjorn and Engineer seems like a fair comparison, as does Mercy and Medic. I'll grant you those two.
Widowmaker and Sniper will play very different I think due to Widowmaker's mobility and her ultimate. Being able to both see through walls and, more importantly, grant your teammates the ability to ALSO see through walls is a game-changer if timed right. She also seems far more capable in general combat than Sniper, making her usable in ways other than strict camping.
The biggest thing, though, that I think will differentiate TF2 and Overwatch is that there are several more abilities in Overwatch that seem to synergize between different characters. TF2 had some of these, with Heavy/Medic being the most common and obvious one, but when I see something like Winston's immobile bubble shield that allows friendlies to shoot out of, on a short range character, I see a game that is designed with such synergies to be practically required to win.