When it could stack slow, yes op.
When it had super slow, yes op.
But it was never that bad at %30.
They removed the slow of the mines after they made a talent that amped the slow effect by %20.
Making them into a %50 slow mines that may effect up to 5 targets a great span apart, yeah wtf. That is like the power of an ult, with 2 charges.
The whole issue with the oppressor mines is that it was janky asf walking around a corner and getting tapped with a harsh slow.
Make the slow application a gradual scaling effect over time, and that solves that issue.
Or the value of the slow to be ever so slight such as %15, that may only scale to %30.
Cause Kinessa does not need a heap of control, just a little bit, enough to synergise with scope to provide enough control with line of sight alone.