I don't think it's over powered.
It has a full round casting time. Either you're vulnerable to interruption for a whole round, or you give up the chance to cast 2 spells if hasted. At higher levels, both the downsides to a full round casting increase in importance.
It is also reflex negates. Do you think evasion is good? How much weaker would fireball be if everyone had evasion? That's the way blade barrier works. If you catch 4 targets and 2 save then you do 30d6 instead of the 45d6 a save for half would do.
Finally, once the spell is cast, the blades essentially become a neutral feature - unless simple destruction of the surrounding area is the goal. The blades are like a lava pit; only the very reckless or the poor sap who gets pushed in take damage from it. Also, since the spell isn't (D), the duration can be very inconvient, possibly barring a critical area for a few hours and wasting time on buff spells.