There have been cases of drawing 2 destinys but never 3 so far,since mostly you would surely dump 1 of them via borz as you have guessed and by having 3 copies of destiny and excalibur(not to mention its grave effect) means i can access them for certain when i need them via borz's eff as selecting all 3 copies means my opponent would certainly choose that 1.Since apart from excalibur you can only control 1 of each noble arm equip i simple choosed to max out on destiny for the reasons i mentioned previously(and the fact that having 3 means i will surely add one via borz's eff).