At some point I start to wonder if the common denominator in all of these healing horror stories is the healer telling the story.

There are so many variables within the DF pool that it's essentially a static randomness. I don't believe that any one person queueing for the same roulettes on the same role is going to wind up with a shockingly unique experience that they aren't responsible for.

If you consistently wipe on big pulls perhaps you need to focus more on yourself and less on your tank. If you consistantly have dungeons taking 20+ minutes with big pulls that others regularly clear 5 or more minutes faster maybe you need to focus on your personal DPS.

Everyone has good and bad days. I'm sure every bleeding edge progression healer could tell a story of getting dps happy in a leveling dungeon and letting a tank die which resulted in a wipe. Those single instances are not anything resembling the majority of DF content for most of us though.

I wish I had something more constructive to add to this discussion but I'm not sure what that is at this point. What I do know is that every person defending the OP's perspective needs to know there are tons of healers out there who don't experience this hellish DF existance and if you consistantly have trouble with things you should probably parse some things and get an idea of where you stand or at least watch some youtube videos of more experienced healers to see if you're missing something.

Tl;dr: Maybe it's you. We all get bad tanks sometimes. Stop whining like it's all the time. If it is all the time then look in the mirror.