Gulf Air's main hub is at BAH, not AUH. However, they are supposed to serve the four cities: BAH, AUH, MCT, and DOH. That's why they operate lots of flights from there.
I donno why are you confusing DXB with AUH: Dubai is not a hub for GF, so why should you see the A330's or A340's right there? GF uses the A320 and 763 to feed the hub with pax. Besides, Emirates is trying to penetrate into Abu Dhabi, so the only way left for GF is Bahrain: After Qatar Airways took DOH, and Oman Air is trying to control MCT.
I think GF should follow Swissair when they chose Zurich as a hub, and stopped major flights in GVA. GF should concentrate on one hub only to survive, at least, competition from EK!
A300, A319, A320, A321, A332, A333, A343, A346, A388, B734, B738, B744, B772, B773, B788, F70, MD11, CRJ700