A pilot should be checking his deferred defect log and if any MGB HUMS related defects are noted he should be demanding to see the trend graphs for his own piece of mind (and question them). No matter how good an engineers pre flight or pilots walk around, We are not able to detect the state of play inside the most crucial part of the machine through normal visual inspection. Only HUMS can do so and if there is a rising trend above a threshold that raises concern then a pilot should be quite within his rights to refuse that aircraft.
1st, why should a HUMS trend be in the Deferred Defects section of the ATL? The only items that should be in there are MEL deferrable items.
2nd, if the HUMS events (if there are any) are within the thresholds, and are being monitored in accordance with the AMM/AMP, and therefore manufacturer's?/Maintenance Organisation's approved protocols, why would you expect the pilot to overide this? Would you apply the same logic to Track and Balance figures, engine HSS vibrations, SOAP samples?