Let’s not even consider chance of getting the item with 2 affixes.
Let’s just assume you need just need to add 2 additional affixes at 30% with tempering.
.3 x .3 = 9% (this is the percentage of getting 2 affixes with 30% chance not 2 affixes with highest value).
Now with the 9% let’s calculate the perfect master work where you get lvl 1, 2 and 3. each with 20% chance.
.09 x .2 x .2 x .2 = .09 x .008 = .00072 = .072%
the probability is way too low especially since getting the equipment you need to start masterworking itself is pretty rare find to begin with.
Set a celling on tempering and masterwork please