There are a number of single point failures on all helicopters - I would say that they are always well 'over-engineered' but the gearbox / rotorhead mounting design of the Puma family has always looked surprisingly weak, whilst history and shear number of hours flown has proven this as a very effective design.
As to live HUMS data, the problem has always been that the systems themselves are considerably more reliable than the sensors, micro-switches and telemetry of a HUMS set-up. Do we want to be flagging warning lights in the cockpit at the rate that engineers will see spikes on the HUMS print-out??