I can kind of understand their frustration to a degree.
I'd be like a Sch just summining his fairy, the Sch auto-following the tank, and then going afk for the next 30 mins.
I'd be slightly peeved as a DPS when the Sch is essentially leeching, and if it were possible I'd rather just have a 3rd DPS instead and have one of the DPS put cure on their bar at that point, but I can't because the Duty Finder requires a job with the healer role.
There's certainly a certain level of frustration when people are putting in effort on a team and someone isn't. It's like those school group papers where one person does all the work and the rest just do nothing.
ESPECIALLY in lower level dungeons like Halitali where a Con/Whm with Stone II is going to be pushing similar DPS numbers as the DPS themselves.
I mean strictly speaking the tank, if able, can just hold hate by doing nothing by spamming flash and the DPS can stop using skill and just kill stuff with their auto attacks. I mean as a DPS pushing extra DPS is optional, right, so long as you clear the dungeon within 90 minutes, but no one wants to take 90 minutes to clear a dungeon.
So yes, I understand a the frustration of your party if you had a good tank that barely took very little damage and you essentially sat there doing nothing. It's very likely you turned what would have been a 20 minute run into a 30 minute run and wasted 10 minutes of the rest of the party's time.
Now I'm not saying you must squeeze every ounce of DPS at all times and have the most stressful run ever because everyone is constantly at 100 HP, but if you are intentionally putting in less effort than the rest of the party...yeah, that's pretty low.
Is it reportable, no, but there are plenty of things that shouldn't be done that aren't reportable either.