played few 1v1 customs games last couple of days after about 2 month pause. I still believe MMM is way OP at least vs toss.
1. toss needs to go for an observer to actually see what terran is doing
2. if yes you need Colossi (long tech path, expensive) or templars (long tech path, cost tons of gas + good micro needed for usage)
3. You can't expand before this (no ramp blocking with force field)
So even if you fend it of your way back in terms of economy.
plus MMM = no micro needed you can basically a-move. It's just so simple, that's why most terrans do it.
mmm is not OP
1. toss can early scout and see what the terran is going for, so that point is moot. plus then can push in a little and test defenses, see what units and buildings terran has. then later the observer is useful.
2. you should of expanded before terran has mmm. its not easy to have a good force of marines and marauders plus tech to medivacs early.
mmm = lots of micro. you have to make sure you dont move your medivacs with your units so they heal more, and you have to shoot n scoot as well.