Only played Vigilance with my Guardian so far, and I'm absolutely steamrolling the Heroics with Jeanne. Just got to level 65 with the level 60 mods you can get from the level 60 vendor. Will be quite some time before I go for KOTFE. Because I have the earlier expansions left to do, and still busy with my class quests and planetary quests. Just started on Belsavis
I've played a lot of Combat Sentinel & Carnage Marauder in the past. But my Guardian is just as fast as them, and has much better survivability to boot. Win/win for me
When it comes to the other disciplines. Haven't tried Focus yet, because Vigilance works perfectly for me. And I have zero interest in tanking, so I'm not going to try that discipline either.