ALL Heroic 2's should be soloable with your companion AT LEVEL (depending on class this currently isn't always true).
Meh. That's not very "heroic". That's just questing in a phased area, and we have plenty of those already. There should be some challenge!
Heroic 4's should be doable with just 2 people with their companions, this isn't true either for all of them. Although as mentioned some are able to be done solo.
My gf and I do that already. Good communication between the two players is key. Even then it's not always a steamroll through the place.
Posters upthread said it best: grouping-to-level just isn't viable for most players, and the planets are deserted now that the rush is done. I agree that there should be more Heroic 2+ and not as many Heroic 4's, or at least move the 4's to earlier in the planetary quest hubs. Little reason to do them when you're leaving the planet, extra content or otherwise.