I don't think Temple of Artemis granting a granary is necessarily an issue. It doesn't need the granary to be competitive; it's just a small bonus for those who plan for it. I wouldn't be opposed to changing it either, but I'm a bit wary of ToA granting a free barracks, because that would drastically change its role in the early game, and would be very difficult to balance with the knobs we have. (I don't like the idea of increasing its cost; that would be another major change to its role, and all the late-ancient wonders should have consistent costs IMO.) If the granary is really an issue, I would suggest removing the free building altogether and increasing its base yield instead. (+3 food?) There's no rule that says a wonder has to grant a building, and the ancient wonders aren't really consistent in what they give anyway.