I hope they do something like that. I personally find it annoying that accuracy is the only actually important [secondary] stat (and only up to a point and in limited content). Variety wouldn't hurt this game's itemization, though it might allow for some items to be gain 'must have' status. Of course, by 'must have' what is really meant is: this item is noticeably better than others. Unless they have no idea how to balance things at all (I wonder sometimes...) it shouldn't be a big problem.

If they adopted the sort of stats you're talking about, what would likely happen is something similar to the current situation -- that is the pool of available stats would still be somewhat limited and as such most sets would have most of the stats present somewhere. Higher item levels would offer the same stats at a higher potency (weighted for what type of item it appeared on and in the company of what/ how many other stats). This would mean that unless you specifically avoided something you couldn't be without whatever killer stat, though you might currently be unable to get the highest level of it. It would also allow you to stack particular bonuses by mixing and matching from different sets (eg. ilvl 150 set has 'blood for blood +2 seconds' on the gloves, while the ilvl 140 set has that stat on the shoes).

I think it would make things more interesting. Granted, unless it was designed by a god or something there would definitely be a mathematically best set, but that's irrelevant. Technically there's a best race to play each class and we all happily ignore that. There currently exists best sets and the vast majority of players don't have them since it requires completing the most difficult available content repeatedly.

They just need to make sure they don't put insanely good stats on something and then never offer any worthwhile alternatives again. Something like TP regen +10 on an earring would likely mean, "I'm never removing this earring" unless they put out another with +11 and so on.