Everyone’s favorite topic! I’m going to argue a couple of points about when nerfs are needed, and not needed, for the game.
Reasons to nerf
1. A character breaks intended gameplay
Example, D3 intends that a match of X difficulty lasts 3 minutes for most characters to use their powers properly. This is the "game" essentially. This character makes matches that are an average of one minute. Invalidates the core gameplay. The ap denial, give and take, damage mitigation, etc. This character needs a nerf.
2. One or two characters make an entire tier of characters worthless.
Especially in a game that has a wide dispersal of characters, and one that wants you to spend money to roster them, this is paramount. Again, a tier is designed with a certain power level and gameplay interplay in mind. You can't lift everyone to the broken characters level, or you break the entire tier design.
-In Sum: Characters which invalidate entire tiers of designs and gameplay need to be taken down a peg.
What Does NOT need a nerf
1. A character is the best in a certain limited element of gameplay
All games will have tiers, or ways to rank characters. In X situation, there will always be a character that is best. Yet this best character does not break the core gameplay or intended design of the game. If a "best" character in a limited area completely overlaps another character, then that lesser character needs a buff to differentiate it.
2. People are tired of seeing the same character
Sometimes certain characters are just popular. That's fine. While an OP character may be incredibly popular, popularity is not indicative of its impact on gameplay.
3. HAX character X is so cheap/beat me/shamed me/etc.
Perception of character power is not an argument. The character may simply be the best at what it is in the situation you were in. The character may be fairly balanced, but have abilities or strategies you did not consider.
Arguments that should never enter a nerf conversation
1. I paid money!!!11111
Irrelevant. I pay money too. And a balanced game will get and keep more players who will spend more money.
2. I like being better than other people!
This is not about having the best character in its class. If you're using a broken character, you're not better than anyone through your skill. Its basically a cheat code in a multiplayer game that breaks the multiplayer game. Hey, I get it. People dope to win. They only care about themselves. But it doesn't earn any respect and ruins the game. Other people get bored and leave. And sometimes people with the broken character wake up one day and realize, "Wait, the novelty wore off and this actually isn't any fun."
Examples of characters that needed nerfs:
Magneto. Used to be a cheap cascade terror that could cause you to win in very few turns.
Sentry: Was the only character that mattered. Blew through matches in two to three turns.