Another thing you may want to consider with this type of progression is the way in which to resolve the Suspended chords. Remember that Dsus2 is the same chord as Asus4.......Or a Dsus4 same as Gsus2.
Even though the Suspended chords are "Quote/Unquote" neither Major or minor in theory, they can tend to lean toward a Major tone even when played in a relative minor key if not resolved properly.
The same would be to avoid playing a III-bVI-bVII progression in a minor key.
Although the chords are correct in theory, this would be the same as playing a I-IV-V progression from it's relative Major key and would most likely make the progression sound Major.
