It ain't impossible on your own, like I said I made it all the way through. But yeah, lot's of high-tailing it to safe spots and cowering in a shield in that case.
The story is told from the assumption of several wizards, no clearer indication of it's intent than that.
Oh, and it's just €10,-. Imho even just the single player stuff is worth it. Currently having a blast, often quite literally, running through it again with access to all Magicks and the gear I picked up along the way in the first playthrough.
Maybe we could give the coop a shot soon, see how/if it works, post some impressions.
* found a staff with lightning immunity. Finally I can cast thunderstorm without vaporizing myself as the first bolt comes down.
** did I mention this thing has been at the top of the sales charts since release?