Does disabling autolinks in the forum significantly reduce save time? If not, does disabling Link Caching (Settings > Options > VaultWiki: Server Settings) significantly reduce save time? How many articles do you currently have? Are there many titles that would be common words?
It takes a while to save, yes, but I am unable to reach a timeout here with the common word 'was' being autolinked, among others. I doubt that autolinking or link caching has anything to do with it, since both of these also occur when the page is displayed. According to some debug output, the entire parse of an article of this size takes about .5 seconds. So I am led to believe that either something is inefficient in vBulletin's validation of the post text (takes about 12 seconds here), or there is another modification you're using that inflates the time significantly.