I haven't noticed it being a detriment to gathering leves. For the ones with an evaluation I can usually get off two of the 250GP abilities that give 50% bonus to gathering success and I always make the 25% bonus from evaluation. Granted, this is only on level 10 leves where I'm keeping my gear up to date and have a 95% chance to gather the normal item and about a 60% chance for the better item without the 250GP ability, but I imagine this would still scale accordingly.

I think the way it currently works is fine as to keep things in the economy in check. If you were allowed to gather too much too fast it'll just tank the prices. (this already seems to be happening)