Have you ever heard of "exposure". In a planned and purposeful way you expose yourself to your fear (in the game of course). You then stay with that fear until you calm down and see that you're still ok. Of course, these spiders are trying to kill you, so you might want to fight back as well... Hopefully you'll still be ok. Well, YOU will be, your character maybe not so much. By the way, I actually learned of this technique, it's name anyway, from Batman unmasked.
Exposure is a useful psychiatric tool, but only if it's monitored and dealt with accordingly. If you have a serious fear of spiders I wouldn't suggest getting the game until you've at least attempted to get over that phobia through traditional therapy (luckily you still have plenty of time before the game comes out).
Therapy might be expensive, but you don't want to translate the perceived "man-killing" aspects of the game to spiders in real life, where you won't have magic or swords to protect yourself.
Whatever you decide to do, don't let your mental health suffer.