Wrack construct is an activated ability that enables extra damage and fort reduction vs. constructs. It costs no SP or ki, yet the cool down is shorter than the length of the effect. Furthermore there is no "buff" icon showing when it's active or expiring.
I can think of no good reason why wrack construct is not a passive ability. Please make it so. Especially considering that the new enhancements are going to make play much more hot-bar intensive.