No, because no Smeargle ever uses Dark Void in singles due to the presence of Spore, and it'd probably be banned in Doubles anyway under Sleep Clause.
EDIT: @above: sorry, half of what you said makes absolutely no sense (what the fuck is a 'suggested use'?) but the point you're getting at seems to be that banning Dark Void is no different from removing it from Darkrai's movepool. However, you simply claim this is a bad idea without supplying any evidence; in what significant way (that is, not 'SD is an item, DV is a move') is banning Dark Void any less acceptable than the Soul Dew clause? The biggest argument against banning specific moves on specific pokemon is that it overcomplicates the ruleset, and it creates a slippery slope (ie, 'Water Pulse Kyogre could be OU!' etc).
@cosmicexplorer: I think what you're basically saying is 'if we ban move x, and move y is categorically superior, we must also ban move y, otherwise we're not banning the move, simply its use on a particular pokemon'. However, consider this: Light Ball doubles both attacking stats. Soul Dew increases SpA and SpD by one stage. In some situations, Soul Dew is admittedly superior, but the net boost granted by Light Ball is much greater, and the attacking stats are arguably the most useful stats to have boosted. However, last generation we banned Soul Dew and not Light Ball. This was because the abusers of Soul Dew were two pokemon with good typing, abilities, BST and stat distribution, while the only abuser of Light Ball was an otherwise terrible pokemon with subpar stats all round when not boosted by the item. If Light Ball had been available to something like Salamence last gen, it almost certainly would've been banned. The reason it wasn't was because of its distribution. The same applies to Dark Void and Spore; Dark Void is available to a pokemon with more or less the best possible specially offensive stat distribution backed by a 600 BST and an ability that makes Sleep even worse than usual; by comparison, Spore is available to three much weaker pokemon. Dark Void is to Spore as Soul Dew is to Light Ball.
You are actually right banning Soul Dew was a slippery slope, however this doesn't justifies creating even more of these.
Also the point of banning Soul Dew was that it would be the reason why the Latis would be broken so we took away the obviously most broken part of them. On Darkrai however you can't say that Dark Void is the reason he is broken maybe its the access to Nasty Plot or the Superb Coverage in just two Moves or maybe its just the near perfect stat distribution.
The easiest and most justifiable thing to do would be banning Dark Void it affects only him and is definatelly one of the biggest reasons for Darkrais brokeness, but why shouldn't we simply put Darkrai in Ubers do we really need another slippery slope would the metagame benefit from a crippled Darkrai? This is the point where i say no, we don't need Darkrai that badly that it justifies creating slippery slopes and as we saw in Gen 4 we never needed this slippery slope of Soul Dew clause either since the Latis were still broken back then.
However if the Soul Dew gets released in Gen 5 wich will propably take some time and we still didn't banned the Latis i don't see why we shouldn't recreate Soul Dew Clause since we actually tested them without SD and since they weren't broken without so why introduce something that clearly breaks them.
In the same way i would say if we only got access to a non-Dark Void Darkrai for some months and it wasn't broken till then, hey why not introduce a Dark Void clause however this is not the case and i don't think we really need even more suspect tests.