I hate to say it, but this is a facepalm moment.
Glyph of Holy Light being upped from 5 yards to 20 then RAPIDLY nerfed back down to 8 yards has to be the biggest WELL DUH moment I have ever seen Blizz come out with. Honestly, what did they expect with a glyph that heals for 10% and each extra one can crit?
5 yards was definitely not enough... But I agreed that 20 yards was way too large. I cant prove that because I wasn't really writing this blog at the time it was on the cards. However, I do think that 8 yards is a little too small for the following reason. There are plenty of 10 yard radius AoE killing effects in WoW. Ice blocks, swirly things, detonate manas, etc etc where you need to stay a minimum of 10 yards apart from each other to minimise AoE damage.
Putting 8 yards on the radius makes MT healing (and helping out on melee) impossible, it also means that if you heal a targeted player, if they were a touch too close you don't land a small helpful heal on the nub nearby.
Flip that to 10-12 yards, and I would be happy. If would cover off the situations where people stood a little too close and copped it but it wouldn't be the OP craziness that 20 yards was. It would also help with MT healing and melee where the boss mechanics don't allow your melee within 10 yards, but being in 12 is still a close balancing act. It would help just enough in 5mans, which is why the glyph was buffed in the first place. People will still need to stack, but not quite as dangerously as with an 8 yard radius. Blizzard is kidding themselves if they think this glyph is like a passive talent. It isn't. It is a TOTAL modification to the spell. Total and utter. But it is way to late to take it out now.