At its heart, Affinity is an aggro deck, but since it relies on synergy between its cards to function, it certainly has a combo component to it
You sacrifice a creature and deal damage equal to its power to any target, while also gaining three Treasure tokens at the beginning of your end step
As a rule of thumb, if an effect instructs a player to look at or reveal a card before it's put into its owner's graveyard, it's unlikely to have received errata
Leonin Arbiter is good, but you have at least five fetch lands where paying 1 life and then an additional to search for a land when you can play Rampant Growth for the same function doesn't make a lotta sense
But Krenko, Mob Boss has a free activation
We also think quite a few other players liked the build which lead into quite a demand (price) for some of the key cards