Don't go for the Quest early on as Reton recommended. I got it sometime mid way through the game, when I had enough spells to quickly kill off the enemy if things got too hot. Alchemist does help though. It also does help to try and complete the Quest on higher levels since there are more enemies. You'll want to also pump some points into health upgrades, though you want the Quest, there's a fine line between doing it safely, and just committing suicide.
@nichodemus is right. Later in game there are far more enemies and you won´t even realize and the quest is yours. I personally had about 750+ dmg taken and the tower had only 200 hp so the quest is super easy when in last levels.
i never collected the award in game so im trying again at the moment but ill let you know after this try and after ill try to delete my game saves and try again
Regarding the flaming spider quest, there was some confusion that wasn't corrected.
Arrows that light enemies on fire DO still exist. In survival, one of the drops are arrows that have a chance of lighting enemies on fire with every normal shot. If you don't manage to get this quest in the campaign, its relatively easy to complete in survival.
I can't event get the knights task quest done. I got the medal ingame, but not quest..blaming it on online saves and all those "failed to save" messages