I just got here, so I'll state my opinion and let it sit.
Mord's Disjunction has two problems that can potentially wreck a campaign. First, there's the obvious item-drain problem. Second, the spell totally destroys the idea that artifacts are hard to get rid of. Why bathe the Grand Gadget of Evil in the hearts-blood of a devil more powerful than Asmodeus if you can just put it into a suitably open space and cast MJ over and over again until it works (trusting the dice not to roll a 1 on that Will save)?
In addition to that, it has one problem that makes it unbalancing in the short term, too... namely its use as an automatic Dispel Magic.
The easy thing to do is to simply forbid the spell... Miracle makes a great replacement for it in any domain that might have it... pretty bad when a spell's less balanced than Wish, huh?
The more difficult path is to nerf the spell in such a way that it still makes a good level 9 spell:
1. I would limit the artifact-destruction effects to minor artifacts, and major artifacts that could be replaced by someone over time. Yeah, you can destroy Thor's hammer Mjolnir, but Odin will just have another one made sooner or later. Irreplaceable artifacts are assumed to beyond mortal magic, even if that mortal is Mordenkainen.
2. Magic items gain a Will save based on the item's caster level - the maker of the item had good Will saves and so will the item. Assume the caster's saves are similar to a PC wizard's or cleric's Will save if the item if the caster level of the item is similar.
3. The magic dispelling effect acts as a targetted Greater Dispel (with a dispel check cap of +25) were cast on everyone in the area. In my opinion, this still makes the spell well worth a level 9 slot considering this ability alone!