Best full group composition

[Jetlag]

I'd be surprised if half your group makes it to 60 before quitting. As someone said before, nostalgia is a powerful drug. Since none of you have played before, there will be a large learning curve. (Even with the level of information available that did not exist before)

My suggestion: strongly assess the integrity and commitment of your companions before attempting to min/max group composition. Having a strong core (as Raev suggested) with suboptimal additions is far superior than building a theoretically strong group composition that never reaches its potential due to players losing interest.
Someone else also mentioned a group composed of powerful duo/trio combinations that can mix/match when others aren't on. That's another smart composition although it doesn't have the best overall potential, it is practical and very functional.

Your group will not be an island. Therefore, don't stress over-engineering the optimal group comp. EQ favors socializing over "skilled gameplay". The "small group" elite gameplay taking down planar content that you may have read about fails to highlight an important fact: Although they are well-played, they overgear that content using items acquired through 30-60 man raids.

Obligatory TLDR for the ADD generation:
You have a better chance of achieving what you want by allowing your companions to experiment and choose the class/play style they enjoy rather than limiting their options to a min/max selection of non-repeating classes.