Sett's W shouldn't have its true damage when cast with no Grit.
The spell is currently... problematic. No, it's not Sett pressing W, shielding himself for 2000 HP, and punching your ADC for 900 true damage. That's just a Juggernaut doing Juggernaut things.
The problem is how strong it is as simple lane harassment.
If you max Q first, you might not see why this is a problem. "You want me to use my main defensive tool, a spell with a 16 second CD, to poke a guy for 90 physical/true damage? What are you, crazy?"
And then you realize how good W max is. A ranged, aoe, 230 true damage nuke on an 8 second CD. Even if you forget the massive shield (which we most certainly will not), that's strong.
Combine that poke with the crazy sustain you get from his passive, and this guy's attrition game is insane. I was running around the tail end of lane phase, backing off from a trade, and between my passive, D-Shield, and Second Wind, I was restoring 17.5 a second. 15 seconds later I was several hundred HP up on my lane opponent and was able to force her to back.
Is it fun? Yes. Is this going to break pro play? OH GOD YES.
2.0, with assassin style dmg and just enough cc to make sure he can get the job done plus some. He is going to be a problem at least for a few patches, then his skin sells and things will go down and riot will nerf him a bit.