Directive 7 was originally designed for levels 47-50 and was therefore the first of the original endgame flashpoints that you were able to enter while levelling up (the next two opened up at level 48). Nowadays it's accessible as a tactical flashpoint from level 15 onwards, as hardmode from level 50, and - as already mentioned - it features a solo mode option as well.
There is a story quest associated with this flashpoint that starts at the main level of your faction's space station and still requires at least level 45 as far as I can tell, called Violent Uprising for Republic players and Immediate Vengeance for Imperial ones. Completing this flashpoint for the first time also awards a title: "the Deprogrammer". It's a bit of a clue: you're going to quell a droid uprising.
Directive 7 is filled with droids, with a couple of cyborgs thrown into the mix for fun. Another flashpoint that's a scavenger's dream! However, there really are a lot of mobs in D7, making it one of the longest flashpoints there is (or if it isn't, at least it feels that way). None of the trash pulls pose any real challenge either, there are just... so... many droids taking up space. For this reason D7 is one of the flashpoints where I've frequently seen people drop out as soon as they saw where the group finder had decided to put them, simply because they don't want to cope with the length of it. Others press on but urge everyone in the group to skip as much trash as possible, which can include crazy antics such as leaping over the rooftops of tents. I was never very good at those and appreciate groups who are willing to do things the "proper" way. There's also a bonus boss that requires you to kill lots of extra trash to be able to click on certain items. People rarely want to do him.
The lesser-known D7 bonus boss.
I suspect that the droid theme is at least partially responsible for the lack of variety among the bosses, who are all droids with one or two gimmicks and generally no personality. There's the first boss, who is a tank and spank with the occasional interrupt to stop him repairing himself and some weak turret add spawns. There's Interrogator, the boss that tries to "replicate" members of your party occasionally, which sounds super cool in theory, except that the "copies" he makes look nothing like your character and are just generic cyborgs. (It was funny though when he bugged shortly after launch and just kept creating endless clones of certain party members.) There's Bulwark, "the one with the buttons (consoles)". There's the one who is similar to the first boss, only that his turret adds are large and dangerous.
The one shining beacon in this sea of mediocrity is Mentor, the leader of the renegades himself, who oozes supervillain personality. When you first encounter him in the form of three assassin droids, he rotates shields around their bodies so that you have to keep switching targets, which is not difficult but can certainly keep a pug on their toes. I also encountered a funny bug on this fight once where the shield on the last droid never really fell off and it would only become vulnerable to attacks for about five seconds once every minute. It took my party a looong time to kill it.
The final fight against Mentor's processing core is pure mayhem, with a giant claw from the ceiling chasing people, big and little turrets shooting the players from all corners of the room, add spawns, and a desperate struggle to destroy parts of Mentor whenever they become vulnerable. Essentially you're fighting the whole room and it feels pretty epic. At lauch I used to find this fight highly challenging to heal due to the high mobility requirements, but these days that should be much less of an issue for most characters.
My impression of the solo mode version was that all the fights are severely toned down, to the point where you could hardly even recognise what some of the mechanics were supposed to do anymore. During a test run on my level 50 Vanguard to see what it was like, I killed the first boss without even realising that I had no healer and that my GSI droid had despawned three pulls ago.
Both Empire and Republic have heard of horrible massacres happening in various places, with thousands of people getting killed by their droids. A group of renegades that calls itself Directive 7 (thus the name of the flashpoint) is threatening to take it even further and wipe out all organic life in the galaxy. Slightly drastic, perhaps? Fortunately at least one of their kind agrees that it is all a bit of an overreaction and has tipped you off that their centre of operations is located on a moon called Zadd. You travel there and meet with your mysterious tipster, a droid called C5-M3 who kind of looks like your standard protocol droid but it's implied that he actually used to be of the medical persuasion. He has no love for the "organics" either but thinks that no good will come of "sinking to your level" by trying to wipe out your kind completely.
You encounter Mentor, the leader of Directive 7, as he controls the bodies of three assassin droids and later find out that he experimented on "organics" by turning them into cyborgs in hopes of "fixing their flaws". After defeating the assassin droids, you fight your way through to Mentor's processing core and destroy it before he can unleash a signal upon the galaxy that would cause millions of droids to turn on their masters.
At the debrief with your faction contact which is part of the associated story quest, it is suggested that C5-M3, who escaped with you, should either be destroyed (Empire) or pressed back into service (Republic). C5-M3 thinks that this is ridiculous of course, as he is a free being and not beholden to anyone, however it is you who gets to make the final call on his fate. I think this is one story where I've actually never picked the dark side option of destroying or enslaving C5 because... this is the guy who just prevented a galaxy-wide massacre and you want to punish him for it!? Are you for real?!
Directive 7 is a great example of how you can use group content to tell a compelling story without making anyone feel like they are missing out if they don't do it, as its narrative is completely self-contained. While the premise of a droid rebellion wanting to kill everyone is slightly reminiscent of cheesy sixties sci-fi ("Killer Robots from Zadd!"), it does play out in an interesting manner, and it does make you wonder about the issue of droid rights. After all, if they are sentient beings, why should they have to be slaves? It's a no-brainer for the Empire of course, where actual slavery is accepted as well, but in the Republic it's at least been a matter of discussion (according to the associated codex entry anyway). The sheer size of the issue does kind of make you wonder however just how the story manages to be this self-contained, and how nobody else in the entire game seems to have heard of these droids that supposedly came close to wiping out the entire known galaxy.
On the other hand, D7 also goes to show once again that long and story-heavy flashpoints don't mesh well with groups of strangers running content through a randomised group finder system. I haven't quite seen it inspire Esseles HM levels of hatred from people who just want a quick run, but it's certainly come close.