Coming off of 5 years experience playing a Priest in WoW and now the 2 months I've had on this commando (about 1 month at 50 now)...you get tired of healing. Especially with ToR's archaic, option-less, ****astic UI for healing. Holy hell...
When asking why healing/tank classes queue as DPS instead, it mostly comes down to the fact that they're tired of it. Do you know how much easier playing an MMO as a DPS class is for PvE content? You know how awesome it is when mobs die in 3-5 skill casts as opposed to 5-10 as a healer/tank? Especially with the companion system, you know how nice it is to not have all the mobs on you while you're trying to both heal you and your companion AND defeat the enemy mobs?
This is interesting to me, as TOR is my first MMO, so I don't really have anything to compare it to. I do have a number of level 50s and have at least 1 dps, 1 healer and 1 tank toon for both Republic and Imperial. So I've at least experienced most of the different playstyles in this particular game.
You mention that the UI for healers in TOR is terrible in comparison to the one for WOW. Out of curiosity, what is different about it? Does it make healing in TOR harder than you would expect? I guess my basic question is:
"Do you not like healing in TOR because it is too easy, or too difficult?"
I do understand what you are saying about how long it takes to kill things while leveling, and that as a dps it goes faster. On most of my toons, I tend to level as a dps for just that reason. On my healers I would respec to heals when I hit Voss so I would have a good handle on it by the time I made it to level 50.
The exception to this was my first tank (Shadow). Being that I wanted to really understand how to play the class, I exclusively leveled in the tank tree, wearing tank gear if possible, with only dps companions out. As tank+dps I felt it forced me to be a little more careful when attacking elite mobs. By the time I hit 50 I really felt confident of what I was doing, and was able to bring my tank into HM operations quickly.
Speaking just for me personally, I actually like all three roles. I like the pew pew pew, but I also really like being a healer. I got good enough as a healer (as well as good gear) that I didn't mind a derp HM FP pug as it was challenging to keep everyone alive, which was fun. I also really like the tanking experience, as it is a different mentality. Playing as a tank my primary concern was keeping the bad guys from hitting my team-mate, followed by dealing with any instance-specific mechanics.
I'm sure that there are a million things that could be done to make TOR better. And perhaps my limited experience with other MMOs makes me look at this one with rose-coloured classes. But I think it's incorrect to say:
When asking why healing/tank classes queue as DPS instead, it mostly comes down to the fact that they're tired of it.
As a matter of fact, my guild had a number of dps-only players who dipped their foot in the healing/tanking experience and every single one of them enjoyed it. A couple of them even stopped playing their dps toons at all, as they found it boring by comparison to playing a healer or tank.