What lady lux said is that, right now, double-melds are the "Needed to Actually Clear Content" gear, whereas that position should be taken by single-melds. Double/Triple-melds should be in the "Makes Clearing Content Easier" position.

Essentially, consider single-meld equivalent to fighting an even-level mob and double-meld fighting a mob with -3 levels or something.
Forbidden Melding IS stronger, it is not, however, required. Or should not be, at least. This way you get a bonus to yourself if you feel like playing RNG Roulette, but you are not strictly penalized for not doing it.