The other thing to note is that they have a very cheap hostel so a preponderance of the guests and divers are very young. Not that that's a bad thing - I had a fine time hanging out with 20 somethings but it's worth noting. Also, a lot of people smoke, much of the dive crew included. They allow smoking all over the boat.
Well to me it sounds like the quintessential definition of LBJ, as far as I have known it : backpacker crowd, booze and cigarettes. (Have I ever been on an Indonesian boat where smoking is prohibited, I don't remember. I believe the first step for being a respectable Indonesian seafarer is smoking a minimum of a pack per day.)
It's true that DDK used to have half of their compound dedicated to hostel rooms, while on the other side of the pooldeck they had quite comfortable double rooms. I stayed in the double rooms and that was a fine option for me and my wife, even in our mid 50's. There was sometimes a live band playing at night and beerpong tournaments until late.
According to their website and since a couple of years they transformed the hostel part into a full 18* double rooms hotel, hence no more cheap dormitories AFAIK.
I don't know which guide you had in your experience, I always dived with either Manu one of the ex-associates, Paul or Nico. All of them made my photographer life as easy as possible, they were everytime flexible on what I wished to see/where I'd like to dive, tried to schedule dives at the best time for the currents. That said I never used their slow boat but either the short liveaboard or their previous speedboat (they now have a faster/bigger one).
On the contrary for Blue Marlin, I had a very poor guide that I paid for not showing me anything at all, being a failure on marine bio knowledge and patronizing me for trying to look for critters on my own. Add on top a management totally deaf to customer requests, even though I was paying for it.
Probably they had the appropriate "look" and felt they were "cool", in the end they didn't deliver at all.
In due comparison, although aiming for the same dive crowd, I thought DDK had much better and more professional instructors (most of them had a 5-10 years experience in diving Indonesia while Blue Marlin had Instructors freshly certified from Koh Tao), DDK also adds tek instruction to their course range.