I'have just talked yesterday with d-link tech support they confirm what i think: dap-1522 in bridge mode don't use standard wifi packet to transmit data, cause as i read in the document i linked they dont' take with it mac address destination and source mac address, so the best performance in the simulate bridging that this device realize probably is when using two dap-1522 one as AP and the other as client bridge with same hardware (that can change in same product with different time production) and also same firmware. In every other combination may have some troubles, worst is if you has an AP from a different brand.