I personally don't see a problem with increased GP regeneration. Add an ability, increase the base, increase the trait. The only functional purpose it has, is to put a time limit on how fast you can collect things.
Part of it is an Anti-RMT measure, i get that. But i think if you get to 70, get above a certain item level, or do a quest, something that takes a little extra time that a dedicated player wouldn't mind doing, but someone grinding up an account just to harvest bot wouldn't want to take the time to do.

Maybe we'll see an improvement at 80, but i don't see a Real problem with restoring a portion of GP after a harvesting session. Fishing is different since you can fish in one location for significantly longer than you can a single gathering point.

Say restore 25 per successful harvest attempt, so a normal node you'd get 100 back, a 6 harvest node would net you 150 back if you were successful all 6 times.
Cordials would still get plenty of use, but they are market prohibited anyway, so that's not going to interfere too much.

Heck, it could even be a charged ability. You build up "stacks" similar to how SE did Scholar's Sublimation in XI, and you can Activate the ability to restore GP. It could be on a 5 min timer or something.

But right, its just a somewhat needless time sink.