40K needs less Warp, not more.
Needs more artillery and bayonet charges...
-Happy Shovel Noises-
As for the lore, 40k is filled to the brim with oddities and various Mary and Gary Sues, Deus Ex Machinas and "all according to plan" moments. Tzeentch is the literal god of it yet within the lore the Alpha Legion seem far and above a Chaos God ability to plot (after all, I could be Alpharius, this post could be Alpharius!) while in other places it becomes odd that somehow things keep going on.
That is part of 40k. Part of it is the immense scale of it. It is very possible that there is multiple systems within the Imperium, both sides of the Chaos Wound that aren't even aware of what is going on. Maybe they had minor upsets or the like but ultimately don't know that Gulliman has returned, Cadia has fallen (whats a "cadia"?) or that anything has happened really. That is the scale. A scale so vast, it often puts other sci-fi in the dirt when put into a "who wins" debate because for any other Sci-Fi, loss of a Billion lives is a cornerstone of an Epoch, a defining historic event spoken of in hushed tones and used in curses most foul that only the gutter-rats use it, a moment that has a name etched into the very fabric of their culture.
For us in 40k, that was the afternoon. For as much there are those within the Imperium that make things happen, ultimately they have had to compete with such obstacles that would eclipse and end any other universe of Sci-fi yet Gulliman calls it a campaign, then notes it down as a success by the end of the year with ONLY a million losses for the Imperium, hey that's a slow year.
The Chaos gods themselves are paradoxical in a lot of ways and I personally like the idea/concept that the "if the Emperor had a text to Speech device" series put on them, the chaos gods are manifestations of emotions but they aren't inherently evil; they just represent the universe's collection state of mind. Khorne is wrathful and filled with bloodlust but he also represents honesty and justice, while he will murder you he will never stoop to trickery to do so. Tzeentch is a force of change and scheming, progress and thought. He is the cunning of the universe made manifest. Nurgle represents resilience and nature, growth and nuturing. I will point out that despite his gimmick of illness, notice how he maintains the health and well-being of his followers and how part of their job is to document new life (plagues and the such granted) as it comes. Slannesh is the manifestation of joy and happiness, the pleasure of living and doing.
The "Chaos" gods are only chaotic because of the universes as a whole. Their lore is even about how they wish to win "the great game" and while the codex acts like there could be a winner there never will be, as their realms are reflections of reality. For one to win, they would need to remove the very idea, concept and reality of mortals having complex emotions. Just not possible, not for the chaos gods just as it was for the Emperor.
Speaking of the Big E, he himself is a victim of his own hubris and inability to accept or contemplate that his creations didn't see themselves as tools, but as sons. As Children. If the Emperor ever had a great weakness, it was his detachment from his humanity and ethical morals most of us would consider. He is himself a deeply complex character who is as rife with Deus Ex Machinas as he is with characterisation that is both telling and obscure all at once. The most venerated icon of the Imperium, the Lynchpin of the 40k universe existence is one of the least understood characters on the stage. As ineffable as he is fallible.
If anything the most ironic point of 40k that many may realise is that the only race "at peace" within it are the Orks. Ironic that the most war-hungry race seems to be the most at peace and content within the universe.
If you want lore questions, one could ask what the Eldar are doing. A race concerned with their demise but yet do not recede from war (which they are perfectly able to do) proactively and focus purely on building their population again. They however fail to see their own failures and move on beyond their past glories, a core sentiment that the universe of 40k explores.
Is 40k lore perfect? No. I mean for goodness sake, we had power armoured marines using musical instruments like guitars as ranged weapons. Orks can literally re-fill their trukks fuel tanks just believing it is full. Would I change any of it? Likely, but then it wouldn't be 40k now...would it? 
I Chapter Master 454, Chapter Master of the Angels of Justice, Warboss of WAAAGH Gubskul, Commander of a Catachan Regiment, Phaeron of a Tomb World, Shas'O to a Cadre and Princeps of a lance of House Taranis hereby pledge that I will not take up any further models til all other prior have been fully built and painted to tabletop standards. There is no time limit for this task, there is no deadline. My oath is to solemnly complete the armies I have now, to see it that they can have their glory. Paint will be stripped from the old in need, thick may it be like ceramite I will see it removed so that plastic and metal alike may see light of new paint. Models yet to be, boxed and in darkness will be assembled with due care and attention. For this task I am permitted to still buy the supplies needed to do my task but not one model more.
http://www.bolterand...one-model-more/ the thread to my oath. My own reminder.
http://www.bolterand...rk-in-progress/ my own chapter
"The objective of playing a game is to win. The point of playing a game is to have fun. Never confuse the two"