Combat Deck refresh times clarification needed

Currently when I go into combat stance and my combat deck appears, the times at which the glyphs are replaced seems random...if I do not use any glyphs and just stand there in the combat stance the spots fill up with glyphs, but the ones on the left side fill much faster than the ones on the right...then after a period of time a glyph will slowly slide down out of sight. But most of the spots on the right side will stay empty, sometimes 2-3 seconds, before a new glyph appears whereas the ones on the left side will have a new glyph appear almost immediately after the current one slides out of sight...but sometimes the spots on the right will have a new glyph appear right away without a delay, but more often than not the right side will have empty spots.

Is there something I can do to change how long some of the spots sit empty before having a new glyph appear...or is the random timer working as intended?

Thank you for your time and assistance.

 

The glyphs are drawn in a set interval (1 per second or so), but if a glyph is drawn that cannot be placed in your hotbar you don't get a new glyph.
Example: I have Aimed Shot slotted in slots 1 and 2. The rest of my hotbar is slotted with other glyphs.
Now combat starts and soon I have Aimed Shot in my first two slots. If I draw another Aimed Shot there will be no new glyph even though my hotbar is pretty empty, because I didn't assign Aimed Shot to any other slot and I didn't leave any slot unassigned.