Actually, a new ring would need to be made for both the Druid and the Ranger... And the Ranger's ring at second and third level would be VERY VERY powerful items.
Also as you put every thing into dext, you still do not get a great advantage on the damage you deal vs the fighter as the str bonus still affects the damage the bow and sword will dish out (as told by Talan for the damage calculation for the bow). When a fighter regularly hits 20's and up without critical vs 10 or 12 with a bow with might even if you hit more often, there is significant difference.