I don't really have problems keeping people alive on my WHM and SCH CD's or not, but some people are really testing their luck lol.

I am good enough to keep people alive just fine, but while leveling my PLD I've noticed how mixed it is with healers too.
Like I had a healer earlier that couldn't keep me alive when I pulled two packs in The Stone Vigil because he/she was afk:ing like 4-5 seconds or even more inbetween every heal and was basically just casting Cure 1 and apparently it was my fault and people claimed that '' those aren't normal pulls ''.
I also had a SCH casting Succor non-stop until OOM in every pull.

Overall tho I dunno, I never had problems keeping tanks alive and still don't.
If anything I have more problems with tanks like PLD's trying to '' help '' by spamming Clemency lol.