The group buffs are all simply more convenient versions of single-target buffs the classes possess. The single-target buffs hit one target and last for half an hour, while the group buffs hit the whole raid (up from one group in BC), last an hour, and require a reagent. The glyphs for the group buffs that have them all reduce their mana cost by 50%, which is a reasonable benefit for a minor glyph.
However (and now I'm finally getting to my point), I think it would be better if the glyph let the buffs last through death, instead of or in addition to its mana reduction. It's annoying to have to rebuff everybody after a wipe, and while the buffs hitting the whole raid will help that a lot, it's still a bit irritating. I don't think it would be imbalanced to only have to rebuff once every hour, and it would make me a lot less irritated on those progression raids or bad pugs. Think of it like flask buffs. And isn't the point of group buffs convenience?