I teach my friends to play using t2 slowking and then move them onto medidoom, then onto ludi.
This is assuming they were old players, who at least had an understanding of the game at base set.
I'm sure if you sat down and went step-by-step, you could teach a player the game with slowking. Go by and say what trainers are for, energy, attacks, plus/minus damage with dre/darkness/tools/etc.
Slowking t2 is actually a good learning deck. It has status, tools, supporters, powers, plus/minus damage from energy, an easy evolution line, etc. The cunning part will take practice, as will the tool selection and such, but that's for later.
I think the theme decks are geared for 10- or people who dont want to take the long time to teachy a player with a strong deck.