Dorian is a fantastic sound. It's unique tonal qualities can be heard from the melodies of ancient hymns long past to the most modern musical expeditions . This unique sound is thanks to a one note deviation from the natural minor scale, the major 6th. Over a blues it adds a bit of spice. Using the 6th note specifically over a minor or dominant chord gives solo lines a bright tone. Just like pentatonics though, it can be tiring playng the same lines and notes after awhile. Dorian does have a close relative though, one that adds a bit more spice and tension to the table.
Dorian flat 9 is the 2nd mode of the melodic minor scale ( another fine substitute at times) It's the same as the dorian scale with the exception of one note difference, the 2nd note. It's a minor 9th, or a flat 9, instead of the typical major 9th. What this equates to is a dark but bright sounding scale with plenty of harmonic color
Here is a comparison of the scales
A natural Minor A, B, C, D, E, F, G
A Dorian A, B, C, D, E, F#,G
A Dorian Flat 9 A, Bb,C,D, E, F#,G
The flat 9th is not the prettiest note to land on. It's downright nasty and harmonically tense, but used tastefully in a lick or melody it can provide a unique alternative to the tried and true tired licks of yesteryear.
I personally love this sound.It keeps me moving harmonically forward in a solo, where I might get lackadaisical of playing the same old tried and true riffs and licks.