By: Susan Doyle and Michele Lerner (washingtonpost.com)Mortgage rates ticked downward this week, rocked by an undercurrent of economic uncertainty, but continue to be elevated above the familiar days when they hovered around 3 percent.The 30-year fixed-rate mortgage averaged 5.25 percent as of Thursday, a dip from last week when it averaged 5.3 percent, according to data released by Freddie Mac. This time...