When it comes to playing this riff there are a few things to consider.
First off we do not have a difficult fretting hand part. The picking hand is what we need to focus on.
In order to play this smoothly I use up strokes for all of the notes and I use down strokes for the muted parts.
The riff is actually a 5/16 and a 7/16 back to back. If you count a long you can hear what I'm talking about.
1-2-1-2-3-1-2-1-2-1-2-3
All notes are played on 1 and the mutes are on 2 and 3. (hope that makes sense)
The reason I've added the muted parts is because they account for the rests that are between the note groupings and creates more clearly the 5 and 7 ideas.