That low bar is there on all servers. I've made it to platinum in a guild of 1 - and I'm sure I could make diamond now and then in one if I put all my effort into it.
The rank and file of guilds has always been such - it's just when it was only GvG for rankings, the guilds that do nothing largely went unnoticed - it was like they didn't even exist because they didn't GvG. Where now they comprise all of gold and below and probably a good half of platinum.
They're not all guilds of 1 either - some are guilds of 80 that just aren't active.
I'd say if you have twice the active guilds (and thus twice the diamond guilds) you probably also have twice the active players