If you're discussing Pact SI, I think your MD protection package is Autumn's Veil just so you have another Green card for your Skyshroud Cutter, the problem with Xantid Swarm is that you have too little of reliable green sources to cast it compared to Autumn's Veil since Summoner's Pact is a no go.

If you're discussing SITES, I think it's a poor choice considering MD Stifle and SB Flusterstorms are in vogue in aggro-control right now, Empty the Warrens just doesn't offer the defensive coverage to storm decks it used to.

If you're discussing BUG Storm, I think it's fine to cut Gitaxian Probe, Xantid Swarm doesn't care how many cards they have in their hand so you can make the deck redundant with a 2nd Ad Nauseam, a 15th land and Chrome Mox(es). Also I think the Fetchland, Dryad Arbor, Green Sun's Zenith and Xantid Swarm package could possibly fuel the Draw 4 deck, but the issue with the draw 4 deck is that it needs to be able to cost effectively play a 2nd creature durring the draw 4 chains to cast a 2nd Culling and you can't do that so well without Summoner's Pact or Kobolds. With Nauseam you just have to get one Culling off, but anway something like ...

4 Tendrils of Agony
1 Ill Gotten Gains
4 Infernal Tutor
8 Draw 4's
4 Green Sun's Zenith
4 Xantid Swarm
4 Dark Ritual
4 Culling the Weak
4 Cabal Ritual
4 Lotus Petal
4 Chrome Mox
4 Lion's Eye Diamond
7 G Fetch
3 Bayou
1 Dryad Arbor

Maybe there is some way to support the D4 chains with like ESG?