The funny thing I remember about being summoner was an avatars ability to gain access to tier elemental spells BEFORE blackmages. I don't remember the exact range but avatars got tier II and tier IV before a BLM and was able to magic burst them first as well. Somewhere this "bonus" was lost and I can't even begin to explain an avatars merit magic spells compared to an ancient magic or tier V elemental spell.
Why has SquareEnix fail to address this issue is beyond me?