I think a really cool stat on items (or even a passive) would be something like:
"Increases Main Stat by X%"
Currently Critical Hit Chance (CHC) is the best way to increase damage in any significant way. Also, it seems like every interesting ability was built around a high CHC to produce its effects (Critical Mass for Wizards, Overpower for Barbarians, or Sweeping Wind for Monks, especially the Cyclone rune to name a few).
Personally I do not like relying on waiting for critical hits to do more damage, even if I do have a high CHC and critical hits happen often for me. I would prefer to just do more damage all the time rather than having to depend on damage spikes to do a lot of damage.
I like how Blizzard buffed rubies in weapons to better compete with Critical Hit Damage (CHD) from emeralds, but average damage still requires high Attack Speed (AS) to be used as effectively as possible.
With the addition of further buffs to Average Damage (AD) in all items and my proposed stat of "Increases Main Stat by X%" I see damage increases falling into 3 major categories:
1) Stacking CHC and CHD
2) Stacking AS and AD
3) Stacking Main Stat and "Increase Main Stat by X%"
This third category is especially helpful for builds that do not require AS, and most of the time hindered by AS such as Zombie Bear spam for Witch Doctors (or any Witch Doctor skill for that matter), Tempest Rush channeling for Monks, and Ray of Frost (Snow Globe build looks like so much fun) or Disintegrate channeling for Wizards.
I would also like to point out that I do understand the strong synergy between AS and CHC, and therefore CHD as well. I would simply like a viable alternative to high CHC and CHD for excellent DPS. I might even go so far as to wish for a day where I can build a viable character completely devoid of all CHC and CHD items. *gasp*
On a separate note I think an epic idea for a Witch Doctor legendary item would be to allow an extra Gargantuan to be summoned, two extra zombie dogs, or the ability to make Fetishes that do not time out (would need a cap on amount summoned for balance). If they were possible on separate pieces instead of being three different legendary off-hands or something that would be even cooler.
After reading the section on Witch Doctor skill balances where the OP mentions the idea of Mass Confusion being able to permanently convert enemies to followers (balanced obviously with a cap and some restrictions on which monsters could be converted) I got really excited.
With that idea, as well as my legendary item ideas, maybe, just maybe my beloved Necromancer Zookeeper build from Diablo 2 could make a glorious return in the form of my Witch Doctor commanding 2 Gargantuans, 6 Zombie Dogs, 8 Fetishes, and 4 converted Hulking Phasebeasts while I sit back and laugh maniacally at the unstoppable force of my army of the undead. That is a world I would like to some day live in. :)
Thanks Gosu for making this thread. There are a lot of great things you mentioned, and hopefully a blue will make their presence known soon enough to confirm that the hard work on this thread has not gone to waste.