At no point of time did the developers state the potions will be available later via buying from NPC for gold.NBG, how many of the potions have you used since the event, if not hoarding? i'm pretty sure the devs stated that the potions and stew would be available after the event arc and be easier to obtain to the loyalists.
i still think the pots are a bit expensive for pvp purposes, due to that they aren't 100% effective. i did the turn in a few times and was underwelmed with their performance in pvp, and waited for them to get cheaper.
If they had stated that, I would not have spent so much time in the past month getting potions. I did not get the blackrock stews because they did state that there will be other method to bond bane dragons later on.
Try using shatter potion when you are in a raiding/defending spawn position where the battle is drawn out.