Defender - 3-4-3
Shadow Walker - 3-5-2
Whipper - 3-4-2
Punisher - 7-3-?
Sentinel - 4-2-?
Medic - 9-1-1
A bit more in detail, defenders can solo pvp quite well and their group synergy is rather high as well given their natural bulk and ability to make people target them (aka, omg there is a giant mech with a sword on my face get it off). The defender's ult is pretty good, I've seen it quite a few times thanks to vix and it is a good ability to get when you have the points.
Shadow walkers are great alone, they can kill that one person wandering off alone and fade away without anyone being any wiser. Their group work is a bit harder to pin down, but usually turns into focus on the people that stray too far from the enemy group and those that focus your medic. Their ult is one of the best in this game imo. It has the ability to make sure one person is out of the fight immediately. Even if it is only single target, it will instantly turn the fight if you take down the threats.
Whippers are great soloist thanks to their innate defense and shields. Can usually 1v2 or more and get away with a kill at least. Given a team, they become unstoppable tanks if their medics are not taken out, not to mention their plethora of aoe cc. And finally their ult. I find it to be the biggest game changer among nearly all of the ults. It has the power to instantly eliminate up to 6 people from the fight. If it doesn't outright kill them, the dot will.
Punishers do not have a very good 1v1. They are made to be the backline support fire, not face tanking that Whipper or Defender. Doesn't mean they can't, but they will have a harder time 1v1'ing than others. Group wise, they are extremely important. The powerful consistent damage they provide is great for any group with a solid frontline defense. I'm not too sure about their ult since I haven't seen it in action except in very cluttered teamfights at titan.
Sentinels are annoying. fast little blighters. Only 1v1 experience I've had with sentinels is Dienasty, and I can definitely see their potential for being duelists. For teams, I say they are an absolute necessity. Their ability to detect sw's and their dps are welcome for any pvp team comp. For their ult, I cannot say I have seen it. I probably have been hit by it before, but I just can't remember it.
Medics are not meant to pvp alone at the moment. The only way I can see them being effective in this way is if they get their blue mech. However, for teams they are a pivotal cornerstone. You need at least one if not two medics in a team. Their ability to keep the tanks alive through even the most heinous of zergs is insane. And their ult is even more insane. It is practically immortality.