I think gleam gathering is too good because it gives much XP and minting value is ok.
In your example you are using diamond hammer but I would use use ruby hammers if you collect gleam in Serpensarindi because those have more base speed and durability. To me also super fast brews feem to be enough, if those are easier to get than mega ones 
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If player needs xp refining gleam is really nice way to do after gathering gleam, and minting could be just byproduct to keep mindless xp hoarding.
I did some xp mining test some months ago with gleam and it seems to be very good. I suppose crazy players could keep pace on gaining 10x 50+levelups in hour with pies, and this would be only gleam gathering xp (refining xp is about same)