I'll wade into this whole conversation.
A previous poster listed a ftp roster that was pretty impressive. The thing I found interesting was the collection score. It was roughly 78. Mine is just a hair under 70, but he has me completely beat gear wise. Probably twice the G12 and G11 toons that I have. I am only missing Traya and IPD. He has eight more 7* toons than I do. I'm not sure how that collection score is calculated, but it appears that massive improvements to your roster won't move the score up too much.
As for who to farm, that is always the question. We haven't been getting as many hints as we have in the past. It is just mainly speculation based on what is being released. So let us look at what are probably the four biggest legendary/Hero's journey characters:
Jedi Knight Luke - he is the rumor king. With ROLO as the login character for September (TB compensation maybe?), this rumor is running full steam again. If he were released tomorrow, you would think it would require CLS, ROLO, Cap Han, R2 and Hoda. However, R2 was used before. There are also crazy rumors like needing Lobot and Lando. My gut tells me he still in the future. If we see an OT Chewie or C-3PO released, I think they would replace the R2 slot or may be needed in addition to R2. Bespin Han and Leia would fall in the same category. Whenever he comes out, he will be a must have toon, so I would prioritize farming his requirements.
Jango Fett - all the bounty hunter love leads to this rumor. Will he require bounty hunters or separatists? If it is bounty hunters, will any five do or do you need Bossk, Embo and/or Sing? Could it be a combo of toons a la Grevious, Zam, Dooku and two others? Of all the rumored toons, I see him as probably the least useful. At this point, as ftp, Bossk is the only thing you could farm (of the newer toons) for this one.
Beckett/Draden Vos - Here you may have a little wiggle room. I would guess you would need a Qira, Young Han, Young Lando, Vandor Chewie and L3. Again, how good is this toon going to be? That is unclear, but my guess is that it would need to be on a scoundrel team. As for farming, Young Han is easy. If you started when they put him in the store you should have him done by now. You have to split focus between Qira and L3. I got them both to 4* and am now focusing on Qira then L3 (134 and 248 shards to go). Vandor Chewie is going to take months without using refreshes (went 0 for 8 on him today). Same with Yound Lando (ditched the Sion node once Lando and Nest were added to ships). Remember, any toon on a single hard node is going to require 105 days to farm assuming 1/3 drop rate and the current 8 attempts per day. That goes up to 168 days at 5 attempts per day. Nest and Range Trooper are your outliers. If either would be needed, I would put money on Nest over Range Trooper. Again, I think either Beckett or Vos will have limited usefulness.
Revan - This will require Bastila, Bindo, Vao, Zaalbar and T3. HK being a requirement would be too much of a gift for a toon of this stature. None of these are farmable yet. When they are, they are going to be my priority. My bet would be that Revan game changing on the level of CLS. I think he would be a huge addition to the current Bastila lead arena teams, giving them a lot more punch. At this point, I think this is the most likely character to be released.
While JK Luke will come someday, I don't think we have all the required characters for him yet. Jango may be the easiest to get if he just requires any bounty hunter. Beckett/Vos seems a likely choice from what is farmable, but I'm not sure he will be worth the effort if you have to choose between him and Revan. Revan seems like a safe bet in the not too distant future and probably the one worth the most effort at this point.
I find it easiest to track stuff on an excel sheet. I try to farm two light side and two dark side hard nodes at a time (zero refreshes). With the cap back to 8, that is going to put a dent in my gear farming. I am farming the Solo characters since it is mainly cantina and ship nodes with just Chewie on a hard node. However, if they sprang a legendary on use in say October, there is no way to be ready as ftp.