Overall I love the game so far and look forward to its continued development. Here is my first round of feedback --

“Bolter and Chainsword”:

The pistols, at the very least the bolt pistol, should allow for the "assault gunnery" skill (i.e. run toward enemies while firing) while in the off-hand slot with a 1h melee weapon. Why? Not only is this an iconic-pairing in 40k, but from a gameplay standpoint the player is giving up considerable defense by ditching the shield. This build would be the half-way point between shield/melee and 2h melee – a mobile melee build that could do a constant tick of damage while engaging their enemies. There clearly would need to be some sort of skill synergy to aid this type of build. Two proposals: 1) give the running pistol shots high suppression damage (which I'm assuming would lower incoming damage if you fired into a group) or 2) scoring a kill with the pistol would give you a temporary melee and/or melee ability damage buff that would further incentive you finishing closing the distance.

Flamer Feedback:

Enemies should always turn into their burnt corpse variants when they die to the flamer. Why? We are dousing them with fiery promethium. Currently the feedback from the flamers feel extremely gamey – like they are simply DPS water hoses rather than fiery death dealers. As a bonus, enemies should scream when they are on fire to remove any remaining doubt that they are burning alive and not just getting tickled to death by a DOT.

Enemy Banter:

I saw an excellent post by Emes where he briefly touched on this and I agree 100%. So much so that I'd say this is perhaps the primary flaw in the game's feeling of immersion right now. Enemies need  to be vocal and have a variety of barks in broken English. Humanoid enemies should be able to call out when they see the player, chatter mid-fight to give the impression they are working together, yell taunts that may or may not be comprehensible, etc. Chaos creatures should make sounds befitting their appearance. Enemy banter would breathe tremendous life into the feeling that we are battling living enemies.

Music:

So far the music is pretty good, but I really hope that it is elevated to “memorable”. Perhaps the best Warhammer music I’ve heard, while not 40k, is Mordheim: City of the Damned’s. An example song from it is “The Stronghold”: https://www.youtube.com/watch?v=tBi9GIEtJgA (stick with it for at least the first minute). Try playing the game with this soundtrack playing in the background. While it isn’t a perfect fit for 40k, and as it was composed for a turn-based game it is very consistently mid-tempo, IMO it carries a weight to it that most game soundtracks lack.

Mini-Map:

Please take a look at the new mini-map in the full release of Path of Exile. Is it incredibly smooth and extremely readable. Probably the best mini-map I’ve ever seen in an ARPG.

Chaos Space Marines:

They should be a much greater threat. Besides the Nurgle Havok (which already are fairly scary in combat), both the ranged and melee CSMs currently feel simply like tanky cultists. I don’t know the exact mix of changes that would work perfectly, but I do believe that they should have far greater agility (i.e. move faster, transition between actions quickly, be able to shoot their bolters on the run while chasing the player, etc.).

Needless Backtracking:

I agree with EMIELREGIS's feedback that the current backtracking is a waste of time. Maps that branch from the center should have some sort of shortcut – whether it’s a 1-way locked door or a teleporter -- at the end of each branch that returns you to the center. The downtime of running a minute or more past empty areas we’ve already cleared breaks the flow of the missions.

Thank you for your time.