Your list is ok, though I would add some finishers that could be recurred without the means of a stronghold in play.
I won a small tournament (19 players) a couple of weeks ago, and I must say that against a lot of deck Gigapede really shines; the only real answer that can eliminate him is Extirpate once it hits the yard, but as you can figure this is not something that every deck can do.

I'd chosen to run a split of 2 Vindicate/2 Putrefy, and in 3 occasion it "saved" me from Extirpate and Meddling Mage. Ok, it's not a radical change, but...

And a Haunting Echoes could also be useful as an alternative finisher; anyway, here's the list that I've used:

// Lands
4 Scrubland
3 Bayou
2 Savannah
2 Polluted Delta
3 Windswept Heath
3 Swamp
2 Plains
2 Forest
// Creatures
3 Wall of Blossoms
1 Grave-Shell Scarab
2 Gigapede
1 Eternal Dragon
2 Eternal Witness
2 Loxodon Hierarch
// Spells
3 Sensei's Divining Top
4 Swords to Plowshares
1 Haunting Echoes
2 Putrefy
2 Vindicate
1 Crime // Punishment
3 Pernicious Deed
4 Damnation
4 Hymn to Tourach
4 Duress

I liked playing this deck, against 70% of the filed here is amazing
Only one thing; there is some hope to beat a Landstill ever? The only game that I lost badly was one against a very solid build of UWR Landstill, and.. well.. I was trying to figure out some answer. Proposition?