It seems that you're using an outdated browser. Some things may not work as they should (or don't work at all).
We suggest you upgrade newer and better browser like: Chrome, Firefox, Internet Explorer or Opera

Is anyone else getting repeatedly oneshoted from full health by the boss in the Witch's first area?

Seriously the balancing on this boss is completely whack.
The nova is hard to avoid. deals crazy damage and the Witch's miniscule range just makes things even worse.