Oh I got WRECKED the first two times trying this (both times before the turn the Voidspawn appears), then I went BS mode and snuck my people into better positions outside the courtyard (for example, teleported my wizards up on top of the bridge), down by the shore that Gareth takes off in the boat at, lured a few of the losers down there and started wasting them...until I caused a Holy Fire underneath the Voidspawn as it first appeared, while also having primarily fire-based weapons.
2nd time around I made sure I could knock off Whatshisfaces armor with a Source based skill so my rogue could tickle his guts before Mr.Snek could come in and ruin the party again (kept everyone on the ground this time, too).
But overall, the entire experience for the game (so far) isn't really all that difficult, other than the EXP being pretty low (and I explored the entire dang island, even the area where the little kid keeps his treasure and even killed the fake-out fire-skele's in the Gargoyle's Maze) and getting to lvl 8 being impossible in Explorer mode without killing anyone/everyone you come across.