Disclaimer: Was on the team before Crytek Austin went south. No longer involved in any way (and haven't been for years!).
Originally, when we were working on this, the internal goal was somewhat akin to a mission-based 4-Player Dark Souls / Monster Hunter w/ a heavier focus on gunplay (though there was quite a bit of melee as well). Weapons were old-school (lever actions, double barrel shotguns, hatchets, with some experimental-for-the-time weapons too).
Damage and difficulty was meant to be incredibly high to force sticking together and of course, teamwork.
You could gather resources during missions (like Monster Hunter) and even find a crafting bench to build upgrades.
We were also working on complex bosses with multiple stages with mechanics that required teamwork to overcome (similar to a WOW boss, but but action oriented).
There was never any talk about 4 players vs 1 boss (like Evolve), so if they went that direction, it's all new to me (but again, I haven't been involved for years). I'm really interested to see what they've done with the original concept. Sounds like it has changed quite a bit.