The gun doesn't go away after an hour, it stops respawning after about ~90 minutes. Meaning that you continue to spawn back with it for that long. If you're able to hold your base the entire time, you're able to keep the gun until you die.
The Credits system was designed for people who are unable to financially support the server are able to obtain these items in other ways. One of the most common methods would be to AFK overnight so that by the time you wake up you have "free" credits. This helps boost the server population during late nights and qualifies as supporting the server, which is why the Dragon Lore is available in this way.
Alternatively, many of the people I know (myself included) have used ingame currency to purchase a Dragonlore by selling that ingame currency for credits/the item itself. During a non-sale period, you're looking at around 15 million (though it could be more or less depending who you find) without having to actually pay any money yourself. You get a weapon, Garnet gets his donation, player gets their money, everyone wins.
Lastly, you're able to obtain these items from Gambling crates from !unbox. I'll say now that this isn't very sustainable, but if you're opening boxes and content with the other drops this is an effective way to gain an arsenal without having to pay physical money.
All that is to say I cannot support the suggestion of lowering the effectiveness of this gun. It's been this way for ages and still lends itself to higher-skilled players. If you're able to scope effectively, there are stronger snipers than the DLore, however it is unparalleled in noscope effectiveness so I do agree it is the most dominant weapon in the game.
However, with all of the options for any player to be able to use it, temporarily or permanently, I don't think it's an outright necessity nor do I think weakening prior donation items is a good strategy. A base built for the USAS is only behind in DPS by about a second tops, and many other automatic weapons make quick work of a raider. Build your base so that they must face away from you when cracking and it's hard for a Dlore user to even assault your base. I could go on about the ways around it but I think I've already over-spoke. I just hope this information is useful in some way