Getting the right mix for your team can be a pretty difficult thing to get right. Obviously your goal is always to have a team that 'clicks,' that meshes together well, can take communication short cuts and can share the hell out of a vision and deliver deliver deliver.
There's a trap inherent in that path of thinking though. It's not as simple as finding a bunch of like minded people that really gel as a group with high levels of camaraderie and etc. OK, that's actually a way to pretty good results in a lot of ways, or at least it will seem like you're getting good results. Your team can work together relatively well, perform smoothly and deliver deliver deliver. What they won't really do, unless they're super-special is innovate.
Think of it like a troop of soldiers. Once they've spent their 300 hours of training to march together, when they're going down the road together, that's where they remain. There won't be the misfit who wonders off the road, runs to catch up, wanders ahead and has time to look at other things, kind of like a lost puppy. Nope, they look really cool, marching in step, making progress, getting where you want them to go. unfortunately, when they get there they're all still wearing the same clothes and saying the same things that they've been saying for the past 400 years.
Don't take this to mean that you should be going out and hiring a bunch of star performers either. Plunk that idea into the same analogy. Now what you have is an unruly bunch of puppies that are tearing off after every little thing that they can find and if, and that's a huge if, you can ever get them to the destination they'll still be an unruly mob with no real delivery. the only way around this is a truly exceptional leader who can hold things together but that person is likely a super-genious, or in this analogy, has a pocket full of steak.
Here's where the diversity comes in. Hire cross-spectrum. Take on a few star performers and some solid but smart performers. The smart performers are going to keep your troupe moving along to the final destination, keeping the goal in mind as they goal. they're there to not only get the core work done but to hold onto the vision in the group mind so that your stars can be guided back to it by honest peer pressure. Maybe not even peer pressure, that feels too directed of an action on the part of the team. More of a peer gravitation. the star performer should see what direction the team is going and be motivated to catch up and help it get there.
An exception here is the prima dona class of star performer. For me, your general prima dona isn't actually a star performer. Because while they can be responsible for some pretty stellar results, they don't consistently perform for you, nor do they bring things forward as a general rule. They are quite useful in cutting edge industries but most of us aren't working in such a place and don't really need amazing sometimes, we need great all the time.
The other benefit of the diversity is that the differences within your team are what help to drive the innovation. When you put different people in a room and start to brain storm, the building of the storm of creativity comes because someone says something that triggers something in another persons mind and then true innovation can happen. if you have over-alignment, then you don't get that spark of difference that helps the entire team create. it will often be your star that gets sparked but it doesn't have to happen that way, idea generation can happen all around. in fact, what your star performers do is help bring all of your core performers up a notch. Now your entire team is producing something of even better quality.
The one caveat here is that fit is still important. your team still has to be chosen so that a base level they can work together amicably. You need some shared experience or like mindedness to keep everything moving along forward. No one likes strife in the workplace. As for mix - like everything else in life, there's a balance here that you have to find. In my experience the mix has been about 70/30 core to star. And indeed there's even room to discuss adding some grunts, juniors or under-achievers but i think that's a discussion for another day.
In the end though, you have to find the ideal mix for your team, maximizing fit where you can and then lead them forward, herding the puppies when necessary but allowing them the room to lift your team out of the doldrums.