It's not the Prep you remember
Depending on the last time you used Preparation, you might not know that it's been changed several times over the past few years. There's no more Glyph of Preparation to add extra abilities to its list, so it resets the same five abilities every time. Offensive cooldowns like Adrenaline Rush and Shadow Blades aren't reset by Prep, but our major defensive cooldowns all are.
Due to talents like Shadow Focus, the extra Vanish from Prep can be a DPS boost. Using Prep to reset Cloak of Shadows is likely to be the second-most common option. Resetting Dismantle, Evasion, and Sprint will probably only be utilized in PvP combat. Smoke Bomb is the only core defensive cooldown that isn't reset by Preparation, which is fine due to its limited but strategic usefulness. None of our talents, like Combat Readiness or Shadowstep, are reset by Preparation either.
More cooldowns are always better
Having a second Vanish available will be valuable for rogues in both PvE and PvP environments. The ability to refresh all of our other defensive CDs is simply icing on the cake that gives us more versatility and durability. Even defensive cooldowns like Evasion and Dismantle can be used offensively to survive attacks while continuing to apply pressure. Preparation wasn't being picked up very often, and so most rogues are going to feel this massive buff immediately. We'll also be able to make use of Prep's extra cooldowns when leveling, as Evasion and Dismantle can allow us to attack mobs more frequently.
Why weren't rogues picking Preparation over Shadowstep before? The fact is that in most environments, mobility trumps utility. You have to be within melee range of your target to be valuable, and Shadowstep was the best way to ensure that we were able to stay valuable. Giving every rogue Preparation for free is a calculated move designed to increase our defensive survivability without altering our offensive capabilities. It wasn't really fair for a defensive cooldown talent to be on the same tier as Shadowstep anyway.
Level 60 tier is buffed to compensate
Blizzard must've realized that rogues were almost always choosing Shadowstep in the level 60 tier. Preparation was given to us as a freebie, but the tier itself has been shaken up. Shadowstep is still a very solid option, but Burst of Speed was reworked and had its cost lowered to 30 to make it more attractive. Due to the cheaper energy cost and the guaranteed movement speed boost, it's definitely a contender. The big negative is that it no longer provides any benefit for us when we're rooted, but hopefully a few extra Vanishes and Cloaks will make up the deficit.
The new talent that replaces Preparation is called Cloak and Dagger, which allows our offensive openers to work from 30 yards away and teleports us to the target when we use one. With an initial opener and two Vanishes, that would result in up to three teleports per fight. Shadow Dance could obviously change this, and I could see subtlety rogues picking this up to ensure their target can't escape the barrage of Ambushes. I think Shadowstep is the better overall mobility choice here, since it can be used far more often and it's both a defensive and offensive teleport. Cloak and Dagger would make a great leveling talent, though, since you're often chewing through targets more often than Shadowstep is available.
We needed a PvP buff
While rogues continue to perform well in raid environments, our representation in PvP is lower than ever before. Preparation becoming a baseline ability will definitely increase our potency in PvP immediately. Because it's an old mechanic, most rogues already know how Prep operates and they know how to work it into their gameplay. Subtlety rogues were running around with both Prep and Step for years, and so this is simply a return to the old ways.
Sneak in every Wednesday for our Mogu'shan Vaults guide, a deep-dive into the world of rogue rotations -- and of course, all the basics in our guide to a raid-ready rogue.