here is my personal expiriace, armada's reccomended drill bit is a 4.1x9.5, atleast it was on my AR6. Because armada is an all wood ski(no metal) you would be fine drilling with a 3,5 bit(smaller diameter). I am guessing the binding ripped out because the holes drilled in the ski were too wide, or not tapped properly.
Most all ski bindings have the same thread on the bolts, so going to a differnt binding wouldnt prevent the binding from ripping out....
tanner Hall uses Peak 15/18's on his armadas so no reason to switch bindings
you will most likely have to redrill 1 or more cm back from center, to be safe. But yeah as said before, if these were brand new Ar7's and you ripped a heel out, there were probably miss mounted the first time... or you just have a Gnarly huge wreck.