Wow, the example is indeed probably offensive to some, and I apologize in advance to anyone who is offended by the fact that I am now going to risk an answer.
I agree with the question's premise that one hell of a is frozen expression that functions syntactically like an adjective. Thus one hell of a is an adjective modifying dick. Interestingly, the expression suck...dick is also a fixed expression, that is, the two words suck and dick build one meaning together, namely 'fellatio'. The meaning is therefore non-compositional.
We can see that one hell of a is functioning like an adjective because it can be replaced by a clear adjective:
She sucks good dick.
In this case, good functions syntactically and semantically just like one hell of a.
This process is a common occurrence in many languages. A verb and a noun together form a noncompisitional meaning that at times can be expressed with a single verb. Consider the following cases:
(1) a. Fred showered.
b. Fred showered for twenty minutes.
c. Fred took a shower.
d. Fred took a twenty-minute shower.
We can see that the same basic thing is going on in these cases. English, like most languages, has varied means at its disposal that allow it to express closely similar meanings. When the verb and the object noun together form the predicate, as in (1c-d), the language can use an adjective to modify the complex predicate. When the predicate is simple, as in (1a-b), in contrast, the language uses an adverbial expression to modify the predicate (here for twenty minutes). Another example:
(2) a. He screwed up terribly.
a. He made a terrible mistake.
We can see the same thing occurring here. The verbal predicate screwed up in (2a) must be modified by an adverb (here terribly), whereas the complex predicate made...mistake can hardly be modified by an adverb (??She made a mistake terribly), but rather an adjective on the noun must be used (here terrible).
Thus to answer the question directly, the mechanism of modification present in the example in the question is a common type of modification that readily occurs in informal as well as formal language. Complex predicates that are formed with a verb and a noun (or a verb and a PP) can be modified by an adjective, and this adjective then behaves analogously to how an adverb behaves when it modifies a verb directly.