Simple DPS percentiles are the most obvious metric, but people who are looking more deeply into things will tend to focus more on a players active rate. A player who can keep their GCD rolling through adversity will almost always be a 'better' player than one who freezes and starts dropping GCDs. They will simply be able to react better mid mechanic.
Ironically in the ARR beta when I was picked up by Solitude (who were one of the top EU raiding FC for a good long time), it was actually my habit of preemptively casting and then canceling if it wasn't needed that got me recruited
A question for you, did you ever see a log of that fight? Healing in this game can be surprisingly deceptive if you're just relying on cast bars.
If we use this P1S log as an example
In that 7 minute fight, the only healing I did with a cast bar was 3 medica IIs (Which is ironically more than I needed really) and the rest of my kit was barely pressured either so if you were listening out for Tetras, watching for Asylum etc, it would have still looked pretty grim.
I actually out healed my co healer by ~20% there and we were both at around 40% overheal.
It's a tricky situation for sure. There's a million different angles and it's gotten to the point now where no matter what Yoshida does or doesn't do, people are going to be mad over it.