@ I assume that running Disk implies running Foil as well, doesn't it?

In order to drop it on turn 4 (The earliest, without crappy cards like Chrome Mox - which I don't recommend to use at this point!), you really have to protect it. Every counterspell (even Cryptic Command, a very clunky card outside of Solidarity).

Therefore you have to run Foil again.

A very important point of Powder Keg is that you are able to drop it before the Landstill player is able to cast Standstill.

On a sidenote: Powder Keg and Call the Skybreaker don't work together very well in the Landstill MU. With Nevy's Disk as the only boardsweeper, you really have to run Rainbow Efreet as the third finisher (for obvious reasons).

Since the disk is way more powerful than Powder Keg, you imo don't have to run the full playset.

// NAME: [TMT] Kleiner Hai, by Nils Müller

// Lands
25 [ALA] Island (1)

// Creatures
2 [US] Morphling
1 [VI] Rainbow Efreet

// Spells
4 [B] Counterspell
4 [AL] Force of Will
3 [PY] Foil
4 [US] Back to Basics
4 [TE] Propaganda
3 [5E] Nevinyrral's Disk
2 [FD] Vedalken Shackles
4 [TSP] Ancestral Vision
4 [IN] Fact or Fiction

// Sideboard
SB: 4 [4E] Blue Elemental Blast
SB: 4 [6E] Chill
SB: 4 [SHM] Faerie Macabre
SB: 2 [LRW] Jace Beleren
SB: 1 [FD] Vedalken Shackles

btw: Is TES still using EtW? Do we still have to fight tokens?