It's hard to notice the W damage since I mostly just use it for the lower cd on Q, although I have indeed noticed the shitty cd. I'll give W second a try, thanks.
It's pretty big, though. Scales with your Passive (50% of your Passive damage) as well as bonus attack speed (50% of your bonus attack speed added to base attack time), but like any DoT it's sometimes hard to appreciate its damage. One of the tricks I like to use is to hit W, move away from my opponent to the outer circle, then engage them when they get in range. People don't appreciate the damage it does
on either side, so they take a few free hits from Wolf before starting the fight proper with me.
And I've been building mostly devourer since like I said I tend to need to carry regardless of my role, although I'm not sure still of a build for Kindred. I tend to go devourer/zerkers/botrk and then... I seriously don't know what to build next on her. The three seem like enough for straight up damage, so what else can I do, just build last whisper?
I tend to go Devourer->BotRK->Berserkers, then depending on the situation I'll get Black Cleaver, Zephyr or Last Whisper, followed by Last Whisper (if I didn't get it already), followed by Guardian Angel/Zz'rot Portal. Trying to consider Phantom Dancer into the build for better kiting, so I'm not completely reliant on Q/BotRK/BC procs to kite people though! BC isn't always built (certainly not when your top laner has it), so your movement speed in fights isn't all that high. The Zz'rot Portal helps you split-push, defend off-lanes, siege harder, anti-siege a bit better, scout, distract, AND it gives movement speed near turrets/portals and pretty good defences, so it's often my go-to item even if not everyone agrees it's absolutely awesome.
EDIT:
Sometimes, you don't get that far in your build. Note that I did have 3.3k bank.
Top didn't need ganks because Darius was beating Fiora hard (who underestimated him for being Silver). Bot lane had Soraka, so they also didn't need ganks. I walked past mid a few times to the point that Vel'Koz didn't dare pass his half of the lane. This has nice results; Lee ends up believing I'm camping mid and he's free to gank bot and top, but as you see I ended up ganking bot/top shortly after he does. This is because I only passed through mid every time I went from Scuttler to Scuttler, building up my Devourer (and finishing it at 15 minutes!). The Scuttlers meant we had good vision, and a movement speed bonus to boot whenever we responded to seeing Lee moving towards one lane and initiating the counter-gank.
Would've been cooler if laners had managed to move accordingly and avoid dying, but every gank Lee Sin performed ended in marginal benefits at best, since there was always a counter-gank initiated. Fun fact: Lee Sin had 100% kill participation and got the most flame from his team.