I'm not sure what you are really asking. D1.1 gives the UT guy some direction as how to perform his/her job, and in some cases they nail down certain things like what transducer to use(size, frequency etc), and if you deviate, then you have to prove your method by testing(just like a prequalified vs a qualified WPS).
What is it that you think is too vague?(be a bit more specific), maybe somebody has some insight that can help you.
Do you have a Level III that you work under who can help?
Are you wanting to know exactly how to UT a PJP or a fillet weld? If so start out by mapping out the joint so that you can see ahead of time what to expect on the screen while scanning.
I'm just not clear what the question is...or if you just want an opinion of what someone thinks about D1.1