Unless they add a way to grind the reputation this will be a non-issue. It will take around a month for the average person to hit exalted to be able to buy it, well after progression for top guilds has ended, and mid-tier guilds will have been doing a generous amount of progression as well.
Anyone who has been stocking up runes to sell has plenty of time to sell them off before raiders start acquiring this item.
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This is absolutely nothing like the Hardened Shell, it is more like weapon oils/whetstones which were Vanilla/BC consumables that were eventually made unusable so they would be irrelevant.