Think of it like this:

Dragon comes into play on stack
use swords to plowshares on dragon

This then puts leaves play ability on top of comes into play ability.
Leaves play returns nothing.
And then comes into play ability resolves removing all the permanents of the sad little dragon player.

Any creature destruction or things like stifle will stop the combo and remove all of their permanents.

Mazes:  They pwn control and combo.  They serve as disruption that slows your opponent down without affecting you as much.

Fetches: The synergy with mazes is terrible.

Elves: I'm not fond of them either but they serve multiple purposes: mana, draw, threat, all in one, albeit being a bit slow.