This is probably in the wrong forum, it should probably go in the musicians forum.
However, the problem with trying to name chords like that it could be several different chords (or parts of chords) depending on the context (especially what the bass and/or 2nd guitar is playing).
For example, using that Darkthrone riff you mentioned:
The notes are A and D, which could be: Asus4 (D is the 4th of A), D5 1st inversion (where the root note is actually the higher note) or even Gsus2 (if the bass/2nd guitar was playing the root note of G). I'm sure I could think up several more obscure chords that these notes could be a part of.
The point is, find out what the context is. So if D is in fact the root note of Transilvanian Hunger (which it looks to be), then the chord progression will be named in that context, because it's unlikely that the first chord in a song in the key of D would be a first inversion of the 4th or a sus2 of the minor 7th. So it would look like this:
And would be named as: Asus4, Am, Asus2, Am
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