So I noticed a wording change from the original PHB in the Glyph of Warding's text that could have potentially overpowering effects for a wizard namely:

When you cast this spell, you inscribe a glyph that later unleashes a magical effect.    VS    When you cast this spell, you inscribe a glyph that harms other creatures.

Now on the surface this seems small but this now unlocks the door for the spell to contain beneficial spells as well as harmful ones for example invulnerability, haste, greater invisibility etc... and by itself doesn't sound particularly broken because in order to obtain the effects you still have to visit the point where you cast the glyph, however with Demiplane you can simply create a room that you can store books in it that contain the glyphs that you can then visit at any time you wish crack open one of the books and boom, max length versions of the spell you don't have to concentrate on because the glyph casts them for their max duration. you just have to pay the meager 200 gold per glyph cost and spend an hour per glyph in this demiplane. Which since you already can cast 8th level spells your not that far from 9th so wish is around the corner and you can just wish up any materials needed for spells. Granted this is a very late campaign power strategy but I don't think this was the Glyph's intended use.

This is not an error. The "harmful" line was throwback to previous editions and the spell was changed in the 2016 official Errata to include any spell you wanted to store. This was because the point of glyph of warding was to have more utility over other glyph spells that focused on damage dealing.

GloW+Demiplane is a perfectly legal strategy because while it can present either a powerful trap or powerful boosts for a single fight depending on use - it takes a LOT of time to get it set up and quite possibly a lot of gold too. Powerful but not broken for the level of battles you will be facing since you're esssentially end-game by now. This also cannot be achieved without using Wish because the GoW takes a full hour to cast and the doorway to Demiplane closes in an hour - the seconds it can take to go from one to another is enough time for the demiplane to close before you finish. Wish, which you cannot get until level 17 and only use once per day, is the only workaround since it lets you ignore casting time. One glyph per day means it will take a lot of downtime to get enough stored glyphs to be truly useful. Also note if you're going the trap route the doorwar is a shadowed one (no line of sight) and even though it's a doorway it still separate the planes so the only way for the glyphs to activate is get the target into the demiplane. So, good combo but takes a lot to make it work and so much time and effort for 1 target or 1 battle, at best, is not convenient.

No typo and not broken.

Okay Thank you for such a quick response. Didn't know about the Errata cool. 

If you have a friend who can cast Demiplane, you can stay in the Demiplane for more than an hour, and then they can open another door and let you out.