4 - Yes, it’s just fine for end game. I was personally able to clear all of Ultimate and all challenge dungeons, as well as Challenger Crucible through 150 and Gladiator through 120 (probably could push if I used ointments) with faction only gear (purposely did not use legendaries I had access to). So definitely fine. And you can obviously make it much stronger with some of the end game builds.
For links for end game vit cabalist builds as well as a leveling guide, see here.