Guys - The OP was only asking if there will be an offline mode :D

Its not one of those mindless ARPGs where you just run in and button mash, there is quite abit of strategy involved aswell, make use of cover, exploit enemy weaknesses, the melee builds prove a little harder at first until you can get decent gear but the game is currently very soloable, try different loadouts and skill sets some work better than others and certain skills are effective against different enemy types. for example 2 of my favorite crusader loadouts are, Sentinel Armor running Plasma Cannon with twin bolt pistols, or Demolition armor running Multimelta with plasma gun. for Crusader melee naturally I run a jump pack armor, I love the 2H Greataxe and usually run a heavy bolter or boler as backup.

Assassin ranged I run Hololithic or Stealth armor main needler for most mobs and flesh elites (esp useful against nurgle enemies) and back up with lasrifle (great for anti-cover and armor)

Assassin Melee build I run Holo or Distortion armor the dual death cult blades backed up by a bolter or lasgun.

If you find you still die too quickly get a decent void shield each activation adds 4000 extra shield points the enemy has to wipe before chewing away at your HP and they can be stacked, so the initial 3 at mission start could be used to give you a whopping 12000 shield.

key things I have found is if you are ranged use the cover, melee try to get +hp weapons.

I am not sure what you are asking. I have only played solo so far and have enjoyed myself. It is a bit of a challenge and I have found myself staring at the ceiling more than once - mainly due to my own carelessness. The environments could use a bit of a change but this is after all an Alpha.

it's a safe bet as it's also got co op and competitive modes that it's a solid no. That and it's going to be a steam game. So double likely no :D

Although I could be wrong.