Evasion has always been important in Limited formats, but in Khans of Tarkir, it's more important than ever. This is mainly because of how clogged the ground gets in this format. High-toughness creatures are everywhere.
With stuff like this out there, it's hard to break through on the ground. Board stalls are common, and that contributes to the average game in this format lasting for nearly 10 turns!
Evasion, then, becomes extremely important. As usual, blue has the most evasive dudes, but most colors have something (except green. Poor green).
(Alabaster Kirin, by the way, is much better in this format than it would usually be. With all the 2/2 morphs running around, this card can get in for damage while also threatening to block. It's been very good in my experience.)
Without evasion, decks need other ways to break through. There are a number of spells that help with this sort of thing, but invariably, they require a whole lot of setup.
In Khans of Tarkir Limited, you should be expecting board stalls in most games. Have a plan to break through, whether that be a game-winning spell, a pile of evasive creatures, or just brute-forcing things with the biggest dudes. Having answers to evasive creatures is also extremely important—when the ground is stalled, whoever is able to take over the air will likely win the game.
I hope this brief call to attention has helped you recognize the importance of evasion in this format. If you've been having trouble closing out long, grindy games, keep an eye out for evasive beaters to help finish your opponents off. And if you have a strategy to breaking past board stalls, please post it below!