I lost my pair when someone inadvertently dumped concrete into an outdoor sump. I don't want to begin to describe what a costly disaster that was.
My second pair I lost when a circuit died for my heaters and the system temp dropped during the height of winter. I had about 30 fish at the time, and the only losses were a pair for Goldflakes, a pair of flame angels and a pair of golden angels.
I would consider them to be nice hardy fish. I have never had them get sick, they have never shown a spot of ich. They have never fought or argued with any other fish. And the two times I have put them together as pairs, the two fish started swimming around together as if they always had.
Now not all fish are the same. When I picked up the Juvi goldflake I have now they also had a beautiful mature goldflake and I wanted both. But they talked me out of it, as the larger mature goldflake was in a tank with Blue Chromis, and in front of us the fish was literally destroying chromis and killing them. So I passed.
My Goldflake now is with a ton of fish, but in the angel category I have a trio of bellus (the smallest female added at only 1"), a 3/4" flame, a pair of golden, a multi-color and a venustus and the goldflake just does it's own thing.
Dave B