In the specific case of the opening salutation I would not insert a comma between the greeting and the name if a comma came after the name, but I would if some other punctuation followed the name.

The following examples all "look correct" to me:

"Hi Mark, how are you?" 
"Hi, Mark.  How are you?"
"Hello Mark, what's up?"
"Hello, Mark!  What's up?"

But the "Hi, Mark, how have you been?" example that you gave looks over-punctuated to me.

In the specific case of the opening salutation I would not insert a comma between the greeting and the name if a comma came after the name, but I would if some other punctuation followed the name.

The following examples all "look correct" to me:

"Hi Mark, how are you?"
"Hi, Mark. How are you?"
"Hello Mark, what's up?"
"Hello, Mark! What's up?"

But the "Hi, Mark, how have you been?" example that you gave looks over-punctuated to me.