Mega Man 4, it's great. In my opinion, it might actually be the most difficult NES Mega Man game. Making up stats for this game was painful. Looking at the stats again after a long time, Pharaoh Man's stats still seem to be off. But let's break it all down then.

Trying to make somewhat fitting stats isn't easy. Sometimes it just means ignoring some of the facts you have and basing the stats on something you feel like is the best. Mega Man 4 was like this. This is how Drill Man's stats would look like if I wasn't restricted to 300 points: 120 attack, 130 defense and 80 speed. They are pretty different in-game, but at least somewhat balanced. So yeah, making up something sensible wasn't easy. Now a few words about some of the robot masters.

Toad Man is really weird, he can deal some major damage, but his AI is so easily destroyed that it isn't even funny. I could have gone with a bulkier build, but I figured that the attack "boost" could give him a niche over other Water robots.

Pharaoh Man, this guy isn't balanced, and you can see it. No damaging weakness at first appearance, super fast, his shots are difficult to avoid. Or then I just like Pharaoh Man a bit too much. Nevertheless, he isn't easy to balance.

As for weaknesses and resistances, it's very straightforward. There may be something to explain, but I can't remember it now. Sorry. Feel free to ask me about anything.