@helvete
Was about to ask if anyone has ever seen more than 3 affixes.

Guess that checks out, then. Though, it did seem like it's
always 3, regardless of ilvl. (Or has anyone seen rare jewels with only 1 or 2 affixes?) It also seemed like you can end up with 3 prefixes or 3 suffixes, which is interesting. (
Edit: I'm fairly sure it's a bug that jewels cap out at 3 affixes: The function does a random roll of 1, and adds 3 to the result, but a random roll of 1 always ends up at 0. The coder may not have realized how this RNG function works. This would also be why pre-LoD has the famous n-1 thing; there's nothing wrong with the RNG function itself, but in most cases it's just not used correctly.)
Well if you use a shield, you'll attack only once per "breakpoint". That's pretty much the trade-off. Whether a shield provides more survivability, I'm not even sure. For decent block chance, you'd have to pump Dexterity
very hard. The formula* for blocking is nasty in 1.07, you need even more dex than you do in 1.14. On top of that, all the dex you pump = vit you can't pump. Also, two attacks means more life leech, possibly making up for the loss of blocking. Or if you meant using a shield more so for the resistances and not so much for blocking, why not Wizardspike?
As for offense, I'm not much of a theory crafter so I don't really know what ultimately is better. My
hunch is that dual-wield is the best, mainly because Crushing Blow is so good, which will potentially be applied twice when dual-wielding. It's also much harder for most two-handed weapons to reach the higher Whirlwind attack speed breakpoints. Maybe if you have some insane craft like WoRG does then you don't have as much a need for all the Crushing Blow, and you can just stack some Shae runes in it to reach a nice breakpoint. I can imagine that with a weapon like that, the physical DPS outshines CB.
Maybe I should also bring up the fact that the +%Damage to Demons from the BK set is not considered an off-hand stat, thus works with Whirlwind. An amazing stat in 1.07 as it is applied separately from other sources. (I'll add that this stat can theoreticlly cause a damage overflow, but I've never investigated what kind of numbers would actually cause one, so I'm not sure if this is something we'd actually need to worry about.)
Anyway, the BK set is basically the "1.07 budget/starter set" for awesome Whirlwind damage because of the relative ease of racking set items. Whether it's actually
the best possible DPS, I don't know. (I hope it isn't, I hate knockback.

)
* : base_block_chance*(dexterity-15)*2 / (clvl*5)