I am probably one of the biggest supporters of using the GFCI/Ground Probe combinations on the forum, but personal safety is a secondary reason I am a huge fan.
If I have a heater or pump fail and allows voltage in the tank, it will also be releasing toxins. Odds are that there will be exposed copper which will corrode much faster if it is energized. Electrical faults also generate very localized heat. This can melt plastics causing toxins to be released.
To protect my inhabitants I want any deranged equipment to be de-energized immediately and I want to know about it ASAP so I can get it out of the water. A GFCI tripping does that for me.
I also understand the concern about reliability. I would never run a larger system on a single GFCI. I use multiple GFCI's to minimize the amount of equipment lost on a trip. My return pump is on it's own independent GFCI. Even if it trips, the power heads in my tank will keep my system alive and healthy for many hours. Much longer than some of the gunk I've seen released from failed equipment.
I don't know anyone who has died from their aquariums, but I do know of problems. An R2R member was working in their small reef (I think it was 20g) and got a shock while standing on a stool. They yanked their arm out as expected, but it caught on the edge of the tank as they fell backward. The tank came over with them and crashed on the floor and they needed stitches from the cut they received. They use GFCI now.