I don't know... I've been running 2 elementalists and 2 physical and I'm having a blast. If they were all magic users, or all physical the battles will be so much more boring!!
The thing is, the main dps is my pyro-geo-poly high wits mage so all the others are kinda support. The other mage is hydro-aero-necro and usually he only deals damage in the form of Blood Storm/Thunderstorm/Chain Lightning or to finish off something the other mage was focusing with basic spells. The physical damage dealers can do insane amounts of damage, but I found them to be better at CCing than any mage, so that's where I focus them... It's nice to receive damage from time to time!
But if I was running a full physical party, I wouldn't use Necromancer as one of the main schools. Necromancer direct damage skills scale with Intelligence and while Warfare scales with intelligence as well while using a staff, the basic attacks deal magic damage (the warfare skills too iirc) and there are very few, very situational Necromancy spells to begin with... I'd only use necromancy for support and Bloodstorm/Grasp of the Starved.
I've seen a build using Bone Widow with max Summoning somewhere. It sounds good, but it's very slow and passive since widows only use basic attacks. Incarnates have access to powerful infusions and are more versatile imo. Still, I'm not conviced about the Summoner gameplay, too pasive for me xD
