To Fuck or Not To Fuck - All the world's a bed, and all the porn performers, merely meat puppets...
A a director, I always start with a plot/storyboard, however I've learned the painful truth, that most porn performers can't act, and many don't even want to try (fumbling their lines, and then asking if they can just fuck).
Therefore, I do not try to get performers to memorize dialog, and instead just try to get them to understand the plot and characters, and to stay in character. This is also why I use a small group of male talent who understand what I am trying to do, and are at least somewhat cooperative/teachable.
Among all of the performers whom I've worked with, Eric Swiss is probably the best in terms of acting ability.
Meanwhile at the Porn "Oscars":
The deluge of porn parodies has actually caused some in the industry to up their game in terms of plot/acting, so it hasn't been all bad. I believe there is an audience for more sophisticated, plot-driven porn, however it is probably small in comparison to the number that simply want to see disposable porn that they can get off to on in a few minutes.
ADG