Tirggered by your question of the advantage of the LM3481 over the LM3488, a little remark, probably not the solution for your over current problem:
C6 should be connected directly to the ISEN pin. It wrong in the datasheet.
See explanation: http://e2e.ti.com/support/power_management/non-isolated_dcdc/f/196/p/216635/763891.aspx#763891