Agree on positioning and melee. I never had any problem in surrounding the mob with other boxed melee. I know some in here don't like it, and opt for a caster dps option, but it's really not that bad, specially with all the changes they made to push.
As for the dps figures, my guess is that at 200-400 range all hybrids/dps/casters will be at similar ranges. Peeps have pre-conceptions on classes, so they assume a 75 zerker/rogue dps might blow a 75 ranger/bard out of the water, but until you start stacking those aa's and getting top-group or some basic raid gear, it will not be the case. And as much as itemisation might favour melee these past years, all it takes is for a caster to gain another 5 lvls, go to a vendor, purchase some basic spells, and smash your melee dps...
My shammy, at lvl 75, with 350aa's, and GoD/DoN raid gear, just breaks the 500dps mark, going all out in a root rot. In group, I wouldn't be able to go all out like that if I was doing other things, but I would bring slow and panther to the table. I have a feeling that until you hit a certain level with the 3rd box, the dps will be a bit flat. Then once AA's are in the 500+ range, and you get good weapons, you will start seeing the pure dps (zerker/monks/rogues) really pulling away.
At the end of the day, there's no such thing as a perfect box, and we tend to just keep repeating our personal preferences in this part of the forums. Not that it's a waste of time, as sometimes that gives us an insight about a class that you didn't consider before. But you have the basics of the trio, a tank and a healer. The 3rd is icing on the cake, and I would go with the one that when you look at the character selection screen, you go: "Phwoarrr, now that's hawt!!!11"