It's an issue when a player can do harder content because they put in the time and got the better gear, but wind up being fucked over by the guy farming act one in blues with 300% MF. That's horrible design over an outdated stat that shouldn't be in the game. What needed to happen, since they're so intent on shoving MF in our face, is have a crafter that can affix MF to a piece of existing gear just like how gemming works. It's hard enough finding the gear to viably do act III, so adding MF as an additional requirement is just a slap in the face.
drop tables for ilvl 63 for act 1 is around 4.8% and its 16.3% for act 3, with act 2 at 9.3%
If im reading that correctly, mf increases the percentages, instead of giving you just more loot with the same drop tables. act 3 is more than 3x the drop rate for ilvl63. so a guy with 300% mf still gets less quality loot than you. and if you have NV stacks, you blow him out the water as he'd have to have 3x the stacks to match you. I think thats more than fair, and if you ever farmed with mf on act 1, you'd know its still a complete waste of time. So if you go into act 3 with any mf, its still much better than act 1.
as for adding mf via gems, i think it makes farming too easy, as it would just add to your already godly gear. there needs to be some compromise to losing an affix to fit mf in.
Thats why I always tell people to go into act 2 with 300 mf, as its much much better than act1, even with mf.