There is a mod, that makes spiders invisible: http://www.nexusmods...tion/mods/960/?
Of course, it is only usable for PC, so I hope, it helps.
I don't have arachnophobia, but I really hate the spiders in all DA games (have no problem in other games, not even with big ones). I don't know why, but I accepted it and use spider replacers in DAO and DA2. So far, the mod works fine, you see the red rings and the health bar, you hear the sounds (which can be bad for a real arachnophobiac, I know) and they toss their web, but you wont see them. I finished the caves at the Stormcoast and it really helped. I hate, that spiders in DA overpower you, which shows them in a really creepy angle - I guess, that is my main issue. I don't like it with other creatures too, but the spiders use that feat more often imo.
There was a scene with my elven inquisitor, when the party jumped up to an cave entrance, but due to a bug, Blackwall, Varric and Bull got stucked midway and my little mage was standing alone in front of that cave. And of course three of four spiders stormed right at me and I got overwhelmed. I survived, thanks to wall of ice and wall of fire (those are btw really cool, if you want to keep the spiders away from your character), but in that case, I was really glad, I didn't see three spiders crawling over me. To not frigthen anyone further: that situation was my fault, if I had stayed away from the entrance, they would have stayed inside, but I had to look in there, while my party was halfway down the hill.