Suggestion -
Make it so the more full a natural resource is the less time each pick takes per piece.
If a salt node is filled up to max it means that it's not a well known node and that even having an alt there isn't really unfair because it's not being contested and there is no race for it. Perhaps in this case it should be as low as 30 seconds per piece. The player will still stand there for a short time and leave a window for the node being contested but in the case that it's a claimed or unknown node it will not be an irritating time sink.
This could mean that an ancient root and mother of pearl could be even longer than 2 minutes since I think they can only give 1?
Another solution would be to make it so there is a set time to harvest a node no matter how many resources there are, like 2 minutes to pick 1, 2 minutes to pick 8, no difference. It stands to reason that a hearthling would scour each crack and crevice of a local resource looking for bits to pick for the same amount of time, each time, and that the picking process would be rather negligible.
Maybe a little system chat message like, "you begin harvesting the node for it's spoils" followed by an animation where the hearthing is actually looking around and picking would make the whole process feel slightly more sensical, albeit pointless and larpy.