Remember to specify clearly that you can only use Death Step as a free action once per round (more times at higher levels). By default you can make an infinite number of free actions per round.

he may ignore all difficult terrain and any obstacles so long as he has line of sight to the area
OK, he can escape a Forcecage as a a move action at first level. Once he gets his hands on a Ring of X-Ray Vision, he can ignore walls. He can effectively teleport a distance equal to his base speed times the number of uses he has - a bare minimum of 200 feet at 16th level, and probably miles if he's remotely optimized for speed. You need to specifically spell out what he can and cannot pass through with this ability, whether he can move vertically, whether it provokes attacks of opportunity, whether he's affected by walking over caltrops and so on, whether he's affected by ongoing area-of-effect things he passes through, whether it gives the normal movement penalty to his hide and move silent checks, whether he can move through keyholes since he can see through them, etc.

Precision damage in addition to maneuvers is a bit excessive. He basically has a vastly improved version of Spring Attack by 4th level, so every round will consist of using his swift action to get to the opponent, striking, and his move action to get away. Or charging and using his swift to move away, if he's readied a maneuver that works on a charge. It's just adding d6s to whatever strike he chooses to use.

He cannot run out of readied maneuvers if he's halfway intelligent. He'll be moving at least his speed every round, and so recovering a strike every round. At 8th level and above, he can also use and recover a boost or counter every round. His recovery mechanism needs to have an actual cost if he's going to have more maneuvers known and as many readied as a Warblade does. In fact, forcing him to stand still for a round would be a better recovery mechanism - still better than a Warblade's, since he can use it to full attack, but resembling something balanced.

Touchsight is extremely powerful. Darkstalker doesn't work on it. the only way to avoid it is being underground, behind total cover, or incorporeal. The closest thing to this power that an official class gets is the Scout, which gets Blindsense 30' at 10th level and Blindsight as its capstone. Don't do this.

As written, Improved Death Step is getting to treat a target as flat-footed once per round, plus gaining concealment against readied actions to hit him. The ability to move other beings with you needs far more specifics. Does it require a grapple check? Does it require a touch attack? Is there a size limit on the creatures you can move? Does this take an action, or is it free as part of the death step?

Acrobatics is excessive for an 8th-level ability, but not broken. Well, except for near-immunity to falling damage.

Free concealment at 9th-level, ignoring most invisibility-breaking effects at 12th, and free displacement at 19th. Though you have free invisibility (50% concealment) from Improved Death Step a lot of the time anyway.

Yeah, drop the called shots.

Permanent [Ex] Freedom of Movement is really powerful.

Now that you can hover, you can fly indefinitely, though the wording of Death Step already let you fly if you could perch on something after a couple hundred feet, or ended next to a rough surface so you could ignore the falling damage.

Unknown movement... no. Maybe as the capstone, or limited to a small number of rounds per day. But Hide checks are easy enough to optimize that this is pretty egregious at any level.

If the swift slayer decides to attack in both turns, there is no penalty on any of his attack rolls due to the use of Deadly Speed (any other penalties still apply as normal).
What "other penalties"? Does this cancel out penalties to your attack rolls from Bestow Curse and suchlike? Do you mean that you make your full attack routine at your highest attack bonus?

Also, there are waaay to many ways to get immune to fatigue (or get +24 to Fort saves and Steadfast Determination) for the save vs fatigue for a few rounds to be an actual limitation. Automatic fatigue for 1d4 rounds would be reasonably fair.