Thats not the only drawback...you lose a ton of stats compared to other options, including Robes of Crystal Waters, Robes of the Lich, Tattered Dreadmist Robe, etc.
The hit is cool I suppose, but there are other ways of getting hit capped without suffering such a big hit.
Im not big on mages, but that hit rating for a lock is especially unimportant as you can spec up to 3% (almost every spec takes 2 or 3% hit in the affliction tree) hit for your dots anyways, and via either the Grand Staff of Jordan or other more common hit rating items/enchant you are easily capped with far superior stats. Furthermore, Int is relativly unimportant to a lock, and any comparable gear that has stam would be better utilized.
To compare:
RoP with 4stats= 14int 4stam 4spirit with 9hit and 16sp
RoP with 100hp = 10int 10stam 9hit 16sp
Robe of the Magi with 6stats = 12int 6stam 11spirit 22sp
Robe of Magi with 150hp - 6int 15stam* 5spirit 22sp
Robes of the Lich with 6stats = 16int 19stam 14crit
Robes of Lich with 150hp = 10int 28stam* 14crit
Robes of CW 6stats= 18int 18stam 12crit
Robes of CW 150hp = 12int 27stam 12crit
Tattered Dreadmist 4stats = 13int 13stam 17spirit 16sp** (forget exact number off top of head)
Tattered 100hp = 9int 19stam* 13spirit 16sp**
The only reason I could possibly see RoP being good is if you really need the hit for some reason there. Hit to gloves, Surefooted, BoA staff, Inscription offhand, Mantle of Doan, talent specs, and others all should yield better overall results.
Ill admit that it looks pretty slick though.