You must have the worst luck imaginable if you're constantly paired up with healers that won't heal. I run in DF all the time and always get fantastic healers that know how to balance both healing and DPS. When I don't, it's because they err on the side of healing more than necessary while not DPSing.

I'm gonna guess what's ACTUALLY happening is you're freaking out and throwing out cures the instant anyone drops below 100%, while everyone else is waiting for them to drop to more 60% where their heal won't massively overheal before healing.

(Also, psst: If you weren't spamming single target heals on all the other parties in the alliance, guess what? The healers in the other parties were healing!)