I think the point of the glyphs that are the same but 1 point less is that you can actually add in an extra glyph or two as oppose to when you had the non master glyph that made it too full for anymore for to fit in. So say you have like 3 points left and have a great set up but you want this other glyphs that's 5-6 points. If there are 3 master glyphs that are similar to the ones you have then you can get those making it -3 points total of what you used and then you can get that other glyphs. So in other ways it actually can be useful.
From: SephCloud | #007 Most master glyphs for every class sucks, unless you're a slayer.
Slayers is a stupid class. Yeah, increasing your endurance by 25 for 8secs by using Death from Above is so useless, along with other glyphs that increase the chance of cooldown elimination for stun skills and increasing their duration for PvP use.
Warrior Glyphs are so bad, you shouldn't roll a warrior at all.