Investor analysts remain skeptical about the biggest mortgage industry merger so far this year, Wachovia’s recently approved $24.2 billion acquisition of Golden West Financial that should raise the company’s origination ranking several rungs. Through its World Savings thrift, Golden West was a pioneer in option ARMs, a product that has caught fire over the past year and accounted for an estimated 8.9 percent of mortgage originations during the first half of 2006...