You make it sound like way more effort than it is. At 110% you can keep the tank up and contribute a significant amount of dps. At like 90% you can maybe throw a holy or 2 out. At like 70% you can scrape by keeping the group alive. At like 60% you wipe. You don't have to give 110% all the time.
Either way, it's not really their fault if it's your healing that caused him to die. Wipes happen, whatever, but don't push the blame. If you can't heal someone that you were capable of healing, that's your fault. Not their fault for taking an amount of damage that you were supposed to handle.
If you ask for small pulls then it'd be their fault. If you just don't feel like putting forth effort and also don't tell anybody that, then tough luck but you caused a wipe.
The fun part is that there's an actual chance to fail. If it's 100% guaranteed that you'll succeed, then why even bother? Just let me click a button for some tomes and save us all some time. I wanna actually have my actions have some sort of effect.