Considering we 2 heal all of firelands hardmode with an average healer item level of 382 or so, and we 2 heal our normal alt runs in ZA/ZG gear, I would imagine 2 healing normal modes would be possible with average skill and competent dps at item level 359 with the nerfs, which is the intended item level for normal mode firelands, and what it was balanced around.
but for heroics, you have to deal with some mechanics, like:
Beth: the distance between your tank and those who soak the exploding spiders might be too big to cover with one healer - plainly a rangeissue
Baleroc: a Healer getting tormented because countdown forced him is really hard to counter when twohealing, since the nerf, healing with three healers is possible and more or less gets you rid of rng.
Domo: Okay, Domo heroic in itself is a joke, but if you intend to take cleaves in further scorpionphases, this might become troublesome, depending on your healersetup and external raidcooldowns.
Other than that, twohealing is not that complicated in heroicmode, certain bosses are even eligible to solohealing, if you're very self-confident