Double Glyphbreak On Witness With Single Buff | Rocket + Still Hunt | Destiny 2: Salvation's Edge 

Once you have the Glyphbreaker buff, you can break two Glyphs using just one buff by shooting a Rocket and then switching quickly to a Sniper to hit another Glyph.
In this video I am using Apex Predator and Still Hunt.
Note that I am doing this solo and it says 2 Glyphs broken :)