Given how difficult they are to get...i don't think a double meld is a good comparison. you can get a good double meld for like 3-4m. or roughly a day of hard farming.
given how difficult they are to get, and the hours required to get them, i'd say it should be worth at least a solid tripple meld.
you have to gather about 21,960 times to get one. Fishing would be the easiest one to obtain, because at least you don't have to run around a ton between nodes. you can find one body and sit.
but even if you are getting 2 catches a minute. you're looking at around 183 hours of fishing. and that's lowballing it by a pretty extreme amount, because it's assuming perfect catches every time. you're probably looking more along the lines of 250 hours. to me that sounds like it should be DAMN near relic status. given that gathering classes don't' really have relics. the luminary stuff should be right up there.
given that crafting is FAR far easier to get and the stats between the two are comparable, it certainly doesn't seem fair to the DoLs.
Saying achievement rewards are not meant to be the best thing ever is fine. but why can't they be? who dictated that all achievement rewards have to be crappy town gear? that's like saying these tools are for botters only because they're the only ones that would actually attempt it given the crappy stats and the amount of time you need to invest.