Rampage does 4 hits per ability use.
So are you counting 44 hits or 44 actual casts of rampage? because the trait only procs when you use the ability, not from each individual hit during it.
Sadly that is how probability works. While the expected outcome would be 3-4 procs during the encounter, the expected outcome is never 100%. Also basing this “bug” on a single trial is bad, like really bad. If you want to see if it is a bug or not, you should test it on numerous trials, not just one.