yes the baneblade is an hyperbole, but the imperium is so big that all is possible. yes patter make things similar ( a lot of IG have the same look as the cadian.) bu in the forge world books is Made clear that a lot of forge world have a different pattern for the things they produce
Not to mention that recruitment for IG is a lot like something you would see out of USSR. There is no choice and you have to go. Most people are pulled out of farms or thugs from hive worlds. They are usually recruited and sent to a strategic defense location. There is a great book out there called "Fifteen hours" and it's about a recruits first 15 hours after being sent to defend a world from an ork invasion. It explains planetary defense pretty well. The warp is also very tricky to navigate and there is always the possibility to die, lose your mind, get eaten by bigger things, and or all of the above. Even through the Cadian Gate let alone willy-nilly with just a random direction... the risk of losing a spearhead of marines through the warp is catastrophic and one I think they will not take. Think of it as something that everyone respects and fears even chaos.
I really wonder how these warp entities that endanger the travelers look like. I mean they are obviously unaligned entities of the warp, similar to the Enslavers, but imagine how horrid something that can eat a bloody space ship looks like. Im sure Nid Bioships look like children toys to these things.
Within the Empyrean, the entities don´t need to look "horrid". I imagine entities within the Warp may look like this (made that one myself with Apophysis):
Yet most that do (Furies, Enslavers, Vile Savants etc) do indeed look horrid. And when talking about something that "eats" your ship one can only imagine a maw of a giant monster.
Furies within the Warp look like angels or comparable majestic beings. Only when they have contact to the real world they become the furies as depicted in the first Word Bearer novel. Even Tzeentch doesn´t seem to look that bad according to Magnus. But the look of the entities of the Empyrean within their own realm differ greatly depending on the author depicting them.
I seriously doubt they look like angels, and i certainly wouldnt trust a Word Bearers depiction of what a angel would look like. As for Magnus, the GW artwork speaks for itself. What some dude made Magnus think in a book (since thats where im assuming you are getting this from) isnt really credible since again its coming from someone on the Chaos side.
The things I described were told by the narrator and not by specific individuals. I should have stated that more clearly obviously. And yes, having read almost every BL novel there is I get most of my info from the novels. So you either accept that there are differing desriptions of how entities of the Immaterium look like WITHIN the Warp or just imagine what you wish, which is also fine of course. My only intention was to point out that the creatures of the Warp MAY look surprisingly different to what you might expect.
Guess we cant really go further than that can we, lets leave it at our individual opinions on how nasty/beautiful the warp monsters are. Imma stick with predominantly nasty.