Blues solos are my thing. I love the minor pent and don't find it boring. What is boring is lukewarm rhythms and not being able to phrase. There is sort a revisionist movement among guitar players who feel that the minor pent is generally insufficient for building and maintaining interest. This is because, I think, guitarists who can only play in the minor pent are probably not far enough along musically to be able to phrase well. In other word, the minor pent is not something bad, it is an indication that the guitarist is sort of still undeveloped.
As an antidote to the minor pent, it is quite common to add the major third, the flat 5th/raised 4th, 2, and 6. If we focus on the minor pent with the added 2 and 6, we get a dorian mode. However, I'll issue a listening challenge. Of the Chicago/Memphis blues guys, when they play a 2, they rarely precede or follow it with the b3. Instead, they seem to substitute 2 for b3. If a play does not do that, and instead plays 2 followed by b3, or b3 followed by 2, the result sounds more like blues-rock than blues. It also sounds more quote/unquote "schooled," and I mean this in a bad way. As a general observation, I feel that Europeans are more inclined to do this than Americans. I attribute this to the different kinds of folk traditions found in the US and Europe.
Everything I said about 2 and b3 above, is also true with 6 and b7.
Now, to test out my little theory, play some blues and use the dorian mode, without regard for whether or not 2 and b3 are played in sequence. Ditto with 6 and b7. Now, play a minor with 2 and 6 used as substitutions, as described above. Your ear will demonstrate whether my little theory holds up for you.
Now, here's another element to this. The minor pent has no semitones. If we substitute 2 for b3 and 6 for b7, we still have no semitones. However, if we play 2 and b3, and 6 and b7 sequentially, then we have semitones. My general observation of blues solos, in the Chicago and Memphis traditions, is that semitones are reserved for b3 to major 3, as well as perfect 4th to b5, and 5 to b5. This is where players use bends to play in the cracks between the 12-note equal tempered pitches of the guitar, piano, etc.
Turning away from blues solos and focusing on melody, you won't find many blues songs of the Chicago and Memphis styles to use anything other than the notes of the minor pent. If the minor pent is itself such a problem for guitarists these days, how do we reconcile that with the melodies that are strictly minor pent?
I refer to the 2 and 6 subs as my little theory, but I want to make clear that I didn't make the first observation of this. Several years ago, someone on a different forum brought this to my attention. As soon as I read it, I immediately knew there was something to it, as I kind of ran through all of the blues solos that I have heard in my entire life. Of course, I didn't literally do that, but when we look back at a ton of music and make a general observation, this is something that musicians do all the time.
The 2 and 6, to me, sound "uptown" and suave, as if the notes are wearing little top hats. Mike Bloomfield talks about these sweet notes a lot in interviews, and attributes BB King with bringing this aspect of the language of blues to the fore. However, one thing that BB does a lot, is use the semitones between 2 and b3, and 6 and b7. By breaking my rule, he is either disproving its validity, or has a unique style. So, if BB can do it, why can't I or anyone else? This difference between breaking the rule and sounding like BB is that he will sit on those 2 notes, and kind of goose them around a little bit, drawing attention to them. But he sure doesn't play runs in dorian.
My hope is that readers of this thread will test these things out, both by playing on their own, and by listening to different recordings. By the way, Texas and jump styles don't follow this convention, in part because soloist arpeggiate chords and hit on chord tones more significantly than Chicago and Memphis guys would.