The saviour's mirage warriors won't seek a new target when using channeling skills, UNLESS the target dies or "disappears" (e.g. goddess of justice's warp). This is very noticeable when using cyclone against a mobile boss, they'll just keep cycloning on the spot where they were initially triggered (it seems to target the position rather than the enemy itself). Blade Flurry has the same issue, except the effect is worse because they never stop channeling and therefore stand still.
The expected behavior would be for the mirage warriors to properly keep track of the target and to stop channeling once there are no more valid targets.
With that being said, the item is still very strong, even for channeling skills. The targeting issues can be helped to a certain extent by repositioning the mirage warriors with convocation (note that this does NOT reset the target for cyclone, e.g. they will cyclone towards their initial target position) or by weapon swapping back and forth to unsummon them.
Thanks for your report, I'll mention this to the team.