Thanks so much for this thread.
It's a massive amount of information so I'll be taking my time to read through it. I've been looking at the breakpoints but I'm not really sure I understand them.
Could you take a look at my profile and give any advice? I've sadly been guilty of one of those buy item when you see it on AH and well probably wasted gold gearing suboptimally.
Here's my profile: http://d3up.com/b/235945
I also use a pair of crappy lacunis +andys with exp gem for low MP farming. Here's what that looks like. http://d3up.com/b/226170
Looking at your gear, you have almost no IAS, which is a huge problem for WW dps. The breakpoints are given in APS (can look on your char sheet for it in game) and it's important to get enough IAS to hit several breakpoints so that your tornados tick more often. Your MH APS without WOTB is less than 1.5, which is very low.
You have a ton of crit (63%) which is really more than you need, and you'd benefit more from dropping some of that crit and picking up IAS. I'd say replace your helm with a mempo of twilight. This will trade the crit on your helm for 8-9% IAS and you'll break even on the HP/str. That brings you down to 3pc IK, which is fine. Your IK chest isn't very good, but your HP is more than fine so it's not a huge issue. Next, I'd say replace your bracers with decent pair of Lacuni's, you don't need a pair with crit so it will be cheap. This will also get you to 24% MS, which is important for WW since it lets you drop an extra tornado on every sprint.
Your amulet is pretty poor. I'd replace it with something that's similar minus the LOH/CC reduction and try to get either IAS or crit damage. You may have to give up some str or average damage to do so (try to keep some average damage on it).
Your weapons are OK. Mainhand damage is fairly low, but that's mostly because of the amount of dps mods on your weapon (that jacks the price way up on weapons).
Your long term gear goals should be (not including the stuff I mentioned up top):
1) get a better MH, as much damage range as possible, probably go with a mace
2) get a good offhand Echoing Fury. EF is fantastic for WW even in the offhand because of the +APS bonus, which applies to both weapons (EF alone will push BOTH of your weapons up a full breakpoint). The stats you're looking for in an offhand EF are decent str, crit damage (either on the EF or on a socket) and life steal. The fear chance won't matter too terribly much in the offhand, but lower is always better. EF can roll native crit damage, life steal, and a socket, pick two.
3) Replace your IK chest. It's not a good chest. Yes, it has high str, but high vit is more important on a chest because you can get up to 300 vit (only chest and legs can get that much). You can replace it with a Blackthorne's, a better IK (really expensive but worth it) or a rare.