To be fair its all dependant on class, spec, raid, etc.
Molten Core is easily soloable by a hybrid class as tank. Its a bit harder as dps since you will lose alot of avoidance and get hit more and is near impossible as heals because theres a healing debuff boss that will screw you over.
Blackwing Lair will vary upon gear. I dont suggest trying to solo it when you are a fresh 80, but a well geared tank or healer or some dps specs (specifically ret) will probably be able to solo it but it would be VERY risky and thats only a maybe.
Depending on which AQ you do, you will either have a good chance or no chance to solo them. 20 should be soloable by now but many of the bosses in 40 man require a raid group. For example the 2nd last boss you CANT beat without at least 2 - 4 people. C'thun should be soloable depending on whether or not he resets when you are in his stomach, if so you cant. If he doesnt reset however there is a chance you can solo him, you just cant let your guard down for a second.
Either way I dont suggest soloing, just because even if you are able some of the bosses have 1mil+ hp which will take a long time to dps down and will either take alot of avoidance or heals to ensure you dont die.