Attacking from Hiding makes the target flat-footed in regards to that target.
Rules Compendium, page 92:
That
creature treats you as if you were invisible (see page 76).
So, just go Invisible (+20 to Hide if you are moving) to negate the penalty.
Now it's a contest between his Spot and your Hide.
After all, there is a difference in just standing in front of the target and attack or trying actively not to be detected to aim for more vulnerable spots.
So, even more reason for 2 levels of Swordsage:
Cloak of Deception.
Also, forcing Balance checks (grease, marbles), Sapphire Nightmare Blade, Flick of the Wrist, Underfoot Combat, having a friend with White Raven Strike and so on.
It's harder to achieve Iaijutsu damage than Sneak, but there are ways.