Aion does have an AH system but you can only access it from cities and towns. Private stores can be opened anywhere. I do agree there is quite a bit of overlap but one helpful application I've seen is someone selling gatherables needed for a quest directly beside the quest-giver.

As for the 30-minute limit, though it isn't mentioned, we're sure this will only be a temporary measure. Once the first free month of Aion is up and populations settle the queues will probably become eaasier to control and the limit will be increased or removed entirely.