I think the issue is not really with the lack of an LFG tool but more with the length of HM flashpoints. In WOW, you get in the queue, you are teleported to the instance and after 30 minutes the run is finished.
In swtor, betwwen finding the groupe, travelling to the instance and completing the run, it takes more than 2 hours. There is not a lot of people that can regularly have such a long game session (apart from raiding which is planified).
In that sence running flashpoints is much less casual than in WOW and why it is so hard to find groups.
This is part of it.
Some of the flashpoints are incredibly long. They need to supliment by offering a "hard mode" on Heroics with a mission terminal that will allow you to pick from all the heroics available with Drops close to HM flash points, but not quite.
The other part is that you have an entire population that got to CHOOSE whether to solo or group for the entire game. A lot of players chose to Solo, and have reached 50 and continue to solo and are not interested in grouping.
But at 50, bioware forces players to group for a LOT of things, so it's a shock to the system that some players want to resist. (Grouping isn't fun for everyone, especially if you're unlucky with a few PUG groups).
So a lot of those 50's aren't logging in, or they're just going about their dailies and ignoring the group requests.
Bioware's method of Forcing players into doing stuff is a method that is about 10 years out of date for MMO's, but it's their first MMO so I guess they have to go back and make all the mistakes that every other MMO developer has made.
Bioware has TONS of existing content that they could add though in the form of Hard Mode Heroics, making the 2 man heroics actually doable with just you and a companion could alleviate a lot of these issues.
It's another choice. Also, some heroics can be finished in 10-15 minutes with the right group of players. So it's a quick in-and-out for casual players.