Too Human will feature four-player jump-in coop and could launch as soon as this year.
"With Too Human, we're trying to seamlessly integrate multiplayer with the single-player," Dyack explained. "If you're really going to do that, you should be able to jump in any time, anywhere and go on a 15-minute mission with friends or play five or six hours straight if you want to."
"In order to do that, the world has to be pretty open and hub-based so you can jump anywhere and come back; very much like Diablo."
Too Human is the first game in an action role-playing trilogy for Xbox 360, and tells the story of an ancient but technologically advanced world based on Norse mythology. You play as Baldur, a god considered "too human" by his peers. Your quest is to augment your abilities using various implants and upgrades, and show yourself to be a true legend.
You'll have the choice of five classes, each designed to complement abilities your friends will have.
Bioengineers will be the healer types; Commandos the long-range and demolition experts; Champions the fighter-hybrid with party buffs; Defenders the heavy armoured fighters to soak up damage; and Berserkers the bear-like warriors focusing on all-out offence.
Each will be hugely customisable with a large skill tree to develop - the most complex system Dyack believes he's seen.
"The skill tree is probably the most complex one we've seen out there and if anything we're a bit concerned that maybe it's too complex," Dyack continued. "It's got a lot of options and we don't want to overwhelm people with it."
"The skill trees include just about everything, you can make different choices and certain trees will occur. They're meant to allow for certain specialization and customisation. So, as an example, you will not be able to max out everything: you're going to have to make choices. A human Defender will be different from another human Defender depending upon the choices you make."
Combat will be controlled using both analogue sticks, in a similar fashion to Fight Night Round 3. You'll walk around with the left analogue stick and direct blows using the right. Ranged combat will make use of the triggers, using your right stick to aim. And the camera will be controlled automatically, zooming out for ranged combat and closing in when you go hand-to-hand.
"If I was to describe how the combat really works the best, people need to think about Geometry Wars. Geometry Wars for shooting and melee combat is the best example because that's essentially the most similar control scheme I've seen out there," Dyack added.
There will be as many as 50 levels to achieve in the first game, and enemies will drop bags full of loot and equipment, just like in Titan Quest, Dyack thought out loud. Too Human will also take huge advantage of downloadable content, with the possibility of new collectables as well as fresh missions to tackle.
"We may want to do some things like give people some interesting armour sets, and there's actually a possibility of enhancing much more beyond that. But I think I'm going to save that for later," Dyack continued.
"The game's been built around the idea of being able to download things. I think with such a cooperative heavy game, that's a must."
It's a world away from what was shown at E3 2006, and Dyack promises the Unreal Engine 3 powered title will run at a smooth 30 frames a second and visually knock our socks off.
We'd hope so, what with enormous amount of time its been in development and the budget its been allocated - apparently making it the most costly game ever produced.
While Dyack remained tight-lipped about a release date, saying the game was still firmly in development, Microsoft bigwig Ken Lobb hinted that we may well see it this year.
Head over to our Too Human gamepage for all the latest bits and pieces.