The deck works by putting damage counters on your benches pokemon, then attacking with aggron for huge damage. This deck also hits gardevoir. Guzzlord is just there to stack damage on.
I have been testing a deck with aggron that focuses on putting damage counters on your bench. (The Deck can be played in expanded, however, by replacing guzzlords with wailord EX)
Pokémon-22
4-2-4 Aggron (CRI)
4 Guzzlord GX (CRI)
2 Nilhilego GX (CRI)
2-2 Zoroark GX (SHL)...
First of all, what other ULtra rares do you have?
Second, Shauna can be used but is not recommended as a N replacement.
Third, I'd recommend pairing the Zoroarks with Hoopa and Umbreon GX. It actually works quite well.