Perhaps, there is simply a bunch of back story we don't know about at this point.
For instance, SOA got me thinking that Kellhus might certainly leave a strange mark if he is another Titirga. I actually don't really believe anymore, if I did, that Kellhus would possibly seek out the Dunyain just to destroy them. Kellhus entered a world ruled by worldborn - any Dunyain who emerges from Ishual doesn't stand a chance.
EDIT:
To add, I'm still all about Wutteat destroying Ishual. I'm not sure blind means blind in Earwa and torching Ishual would take nothing of Wutteat's strength. He did just lose a fight to a Quya and a Wizard... I guess... so maybe he just wanted to spaz and destroy something on his way back to Golgotterath.