I'd say monsters seem in general to be rather more accurate than they ought to be, though the Wall is by no means intended IMO to be done while seeing the barons (IMO, if you wait to see the BOH's before you fire that launcher, you're making a big mistake in tactics). Your actual best bet with the Wall is to head for the top of the screen and shoot your rockets towards the bottom-left corner of the screen (about 7 or 8 squares away from the wall should be plenty space). With any luck you'll damage the Barons quite a bit before you ever see them, and because you're not aiming for the middle/upper section of the screen there's not much chance of accidentally blowing up the advanced launcher or backpack even if you miss the barons (you'll probably blow up some rockets, but that's a lot better than losing the launcher/backpack). Also, you can only put 4 mods on an advanced weapon without any Whizkid skill, and you can only put 3 of each type on a single weapon (max modding for an advanced weapon is 3D, 3S, 3R, and 3M, and you need 2 levels of Finesse and 2 levels of Whizkid to get that), so you couldn't have used all those mods anyway. :)