People always have an excuse as to why balance isn't necessary:
Single player: "Ohh, it only affects me." Even though imbalances can lead to you getting bored faster.
Co-op: "No player-vs-player so it doesn't affect players." Even though it leads to certain classes/weapons being overused and others get left in the dust.
Multiplayer: "Everyone has acess to the same stuff." Even though not everyone wants to use the same OP stuff to not be at a disadvantage.
I stick by the notion that balance is essentially, regardless of SP, MP, co-op. In one way(s) or another, imbalance does damage the game for you, for others, or for both.
As for the whole, "Don't nerf something in ME3 because I haven't even gotten it yet," that's not peoples' fault for wanting balance. Its the developers' fault, if anything, for incorporating a gambling system for unlocks. I've gotten 8 PSP since the Earth DLC. How many new weapons/characters? None.