Inq ward single target on break slow currently scales at 10%, 12%, 14%, 16%, 20% for it's 15 second after final hit barrier break duration (n/a if ward duration decays without hp broken)
my gobin math indicates that excluding an enemy with an attack delay of one second, the scaling is essentially irrelevant.
the result of the 10% slow is basically the same as 20% across a spread of 1-6 second damage delay attacks within 15 second duration

tldr 15s duration too short amongst it's other application mechanics woes
suggestion: change ward duration and duration slow to both be 30s.
have it apply the first time to ALL mobs that attack during the barrier duration.