It has a short internal cooldown of 0.05 seconds on different targets.
Meaning that you cannot trigger Tiamat procs on different enemies more than once every 20 seconds.
You are free to trigger them as quickly as possible on the same target.
It just means that there won't be a cascading ripple effect if you apply on-hits to twenty units clustered.
Let's say I have 3 champions in front of me. If I use my normal Q how many procs do I get? If I use my Dragon Q how many procs do I get?
Does this also apply to Nocturne's passive?