Against a prepared foe, any golem is a non-threat. Acid or alchemists' fire are so cheap, so effective, and so readily for sale, and golems have no defense against them. The reserve feats would make golems equally ineffective against even unprepared foes.
I'd revise the "magic immunity" to give golems immunity to all non-magical energy attacks, and immunity to all magical energy attacks except as noted in the description.
As written, a clay golem is healed by Acid Arrow or black dragon breath (both magical acid), hurt by regular acid (non-magical), hurt by alchemists' fire (non-magical), hurt by red dragon breath (magical no-SR), and immune to Fireball (magical w/SR).
As I'd change it, the clay golem would be healed by Acid Arrow and black dragon breath and immune to everything else on that list.