I think it depends entirely on your experience, class and gear level and, as such, you aren't going to get many reliable replies. Granted, those that do reply are probably going to be some badass healers :P
What class were you using? I'd imagine that hpala would be the easiest but anything but resto shaman should work fine really.
So ye, if we're talking enough hybrids/raid cds and really solid dps I'm convinced that any fight could be solohealed. For iron qon having 7-8 dps (could have a prot solo tank it as well) would make the phases really quick meaning that you'd have cds to chain through entire p1 (which definitely would be the thoughest part) and that he wouldn't stay alive long enough for his fists to hurt in the last phase. Megaera would probably be more difficult, more dps doesn't really make the fight much easier healing wise (unlike practically every other encounter). However going brbrbr and having enough raid cds (especially things like tranq, ve and ancestral guidance) for all rampages should probably make it doable. Admittedly having some silly line-up like 2 prot paladin tanks and a few dps priests, druids and/or shamans would probably make most fights way easier than 2 healing them in a normal line-up, so we'd have to draw the line somewhere for it to be remotely challenging.
Apart from that I don't really see a difficult fight. I've pretty much solohealed jin'rokh, horridon & primordius as disc. For jin'rokh you just need some cds for storm, for horridon just burn him and ignore jalak (he'll get like 2 cries off), primordius never gets any significant amount of stacks with that many dps (though some luck with mutations will be handy). Council, tortos, ji-kun, dark animus, consorts, lei-shen should all be easy/very simplified by the massive dps. I could see durumu being hard with some line-ups, but if you have two paladins with bops the healing requirement suddenly becomes much easier.
Jin-Rohk would be easily soloable aswell as twins too, other's would be more difficult. Lei shen isn't too hard to heal, I solo healed the last phase when our other healer died in our last run so ye, not difficult at all (Will need hybrids for transition though)
Jin'rokh / Horridon / Council : Shouldn't be a problem as long as you have good dps who don't take unnecessary damage.
Tortos / Megaera / Dark Animus / Iron Qon: Seems extremely hard. Might be doable with multiple hybrids using cd but I wouldn't count that as solohealing
Ji-kun : Easy as long as your dps doing birds can keep themselves up during quills (we do this with a moonkin or ele sham and it's enough to keep them up)
Durumu : Seems hard because of the tank debuff requiring a lot of healing. Maybe doable with a lot of BoP on tanks.
Primordius : Should be quite easy as long as he doesn't get Ventral Sacs
Twins : Seems very hard. Would require bringing Lu'lin very low hp in phase 1 without killing her and then bringing Suen very low or killing her in Phase 2. Even with that it would require quite a lot of healing.
Lei Shen : Hard but should be doable if he gets killed quickly in phase 3.
solohealing consorts is extremely easy, we ended up doing it on alts. 1 pally tank, 1 pally healer, 8 dps. hero in p2 to bring the sun bitch as low as possible (or kill it). think we had her at like 10% when p3 started.
jin'rokh, horridon can be done, id say council too. idk about megaera (if you go green red green red green red it's a buttload of raid damage, if you kill a blue you might get your healer target by the ice beam so no heals for a few seconds).