When using Replicated Menace on a non-golden Mechanoegg the 8/8 raptor spawns first and then the three Microbots when the minion dies. When making this non-golden Mechanoegg (with magnetic Replicating Menace added) golden by getting a tripple, the deathrattle order is reversed. Instead the three Microbots spawn first and then the 16/16 raptor. This bug makes the combination pretty much useless, especially together with Baron Rivendare since your entire board gets filled with 1/1 Microbots instead of two 16/16 raptors.
I guess the “appropiate” and consistent behaviour should be the raptor spawning first, no matter when the Replicating Menace gets added to the minion (before or after making it golden). I have not been able to verify, but I am pretty sure adding a Replicating Menace to a golden Mechanoegg after making it golden still spawns the 16/16 first and the Microbots second.