Hm.. correct me if I'm wrong, but isn't the standard number of gathering attempts for the diadem nodes 5 (normal) or 10 (unspoiled)?

I didn't spend a lot of time there yet, maybe an hour at most. But I always ended up with a multiple of 5 in my inventory after finishing a node.
With no bonus or buffs, I'd have 5 of the mat after a normal node. If I had +2 gathering yield buff, I'd end up with 15 after the node (3x 5).

Wasn't difficult to leave the diadem with stacks that were all multiples of 10 at the end.