Regarding legendary items -- something discussed significantly already but which I hadn't personally analyzed -- my gut response was that it's silly to obsess over orange colored items, but then I decided that, while irrational, most of our enjoyment of this game is silly and irrational, so this complaint is as valid as many others.
I'm sensitive, however, to making blues completely worthless again, and yellows extremely uncommonly useful, as was the case in Diablo 2. Any blues that dropped were not even looked at; I instantly vendored them. So this would be taking the current problem to the equal and opposite extreme.
Instead, I think the ideal solution would be something like this. I'll use simple numbers to explain the idea:
Legendaries are extremely rare, with only a 1 in 1000 chance of dropping, but are almost always very good.
Yellows are fairly rare, but less frequently useful. Yellows would be 1 in 100 chance to drop, but only 1 in 10 is useful.
Blues are quite common, but very infrequently useful. Blues would have a 1 in 10 chance to drop, but only 1 in 100 is useful.
The end result would be that Yellows, Oranges and Blues all have a 1 in 1000 chance of being useful, but reach those results in different ways. This seems ideal to me, so that each type of loot has a different value to it and none of them is completely worthless.