6 months is the price to pay to develop HD models and is not exactly horrible if you have a timeline of content, gear set concepts, and story planned well in advance. Which is what all MMOs do and why it seems (to you) that there is a constant flow of content and gear and that it seemingly does not require that much time.
MMOs have these development plans even before they launch. FFXIV did not have this luxury being that it's direction completely shifted in January.