Generally speaking, any CRPG game with a huge complexity of combat options and multiple characters needs some kind of pause function to make it playable.
With a single character, I don't think there needs to be a pause key - especially when it is possible to set the F-keys to give you numerous different options if you so desire, as is the case in DD.
A fully turn based game is as undesirable in either case as a turn based RTS game, and for much the same reasons - the idea is to create, as far as is possible, a fully immersive experience that draws you into the world.
The idea of people taking turns in combat is so ridiculous that it only works for CRPGs where combat is NOT an important part of the game, but where the main emphasis is on strong characterisation and the development of the plot and the relationships between characters.
Any game such as DD, where there is a very strong emphasis on combat over characterisation, really requires a real-time combat system to work - the more so where there is only a single character to work with.
The only CRPG I have ever seen that gets the balance right between combat and characterisation is Planescape: Torment. Every other CRPG seems to strongly emphasise one over the other.
In games such as Final Fantasy 8 the combat exists only to give items and experience points to the characters. The main emphasis is on the developing story, and the way it affects the lives and relationships of the characters. The characters learn and grow as people, and their relationships with each other change and grow over time. Whole sections of the game are character-driven rather than plot driven.
In games such as Diablo 2, the plot only exists as an excuse for combat. As such, the combat system is far more fluid and sophisticated, and requires quicker reactions and a degree of tactical thinking alien to turn based games (Like: if I stand on this side of the river I can shoot them all without getting hit - as a very basic example)
Any game where the emphasis is primarily on combat over characterisation (As DD is, let's be honest) that is also turn based would be so tediously boring as to be unplayable.
With very few tactical options, no swift reactions required, and no characterisation, why would anyone want to play a CRPG at all?
