The problem with Heroic 4s and why nobody does them is because there are TOO MANY of them on one planet to the point where people like myself just skips them to keep the pace of my planet/class story level.
I hate questing. It is utterly boring. Even in this game, and especially once you did the non-class quests on both empire and republic. In "that other game" the times I have to quest are the most boring times. Now, I do like PvP in SWTOR (not very much in "that other game" esp not whilst lvling). So I tend to do WZ, FP, or H2/H4 (H2 I can usually solo). Less H4 would mean less content for me. You see, non-class quests are almost always same. And class-quest too if you reroll to same class.
People do Heroic 2s in groups because it is easier to group. Two tanks can group together and one can bring a DPS companion and the other can bring a healing companion. However, for a Heroic 4, you have to spam chat to find 2 DPS, 1 Healer and 1 Tank. And it is always hard to find that 1 healer. So imagine trying to do this 4-5 times on one planet!
On a planet you can still quest. Once group full you need to gather together. You also have emergency fleet pass (and if you got authenticator you got 1k credits fleet pass with 1 hr CD; recommended!!).
Having leveled a char as healer from 1-50 I can safely say I tried my best to get in groups but 1) I like challenge instead of faceroll. This means I try to be not overgeared/overlvled and we may wipe; it is hard to find a group of mature people. Often I get ADHD kiddies who want "fast group spacebar lolol" instead of a group of mature, relaxed but good players who communicate when required (e.g. "my first time here" or "how do I tank this boss" or "I will mark don't pull yet"). Actually, it was hard to get a group past l30, and I really tried.
I believe around l40 people just do WZ and use "PvP" gear from there, especially on low pop realms. I did not now this on my first character (which I lvled up as healer from 1-50, and did NOT do much PvP on) so around l30-35 there was not much for me to do but quest (solo, as healer, goes slooowwww).
Give us dual spec and people will more likely have a DPS and healer spec. DPS spec to level. One possible problem with that is the healer may not be used to healing.