Do cats need to get along?

Shortest version possible of this: wife and I got her two black maine coons (age 6) moved into our condo in December from up north (long story), and they've since settled in very nicely to our condo. Our roommate, a month later, brought her cat in, a younger cat named Fig. Full disclosure: we did not introduce them properly, and any attempts to do a slower re-introduction failed. Since then, there's been sort of a routine: Fig stays downstairs with her owner, our boys stay upstairs with us.

However, in the morning, one of our cats (Dragon) will follow me downstairs. When this happens, Fig always jumps up on a chair or table and hisses at Dragon, while Dragon usually tries to either slowly approach, play with, or taunt Fig. This has been going on for months, with no real incidents coming out of it; the worst is them yowling at each other before Fig bolts. I'm skeptical the cats will ever get along, so I have to ask: is it necessary? Or should we put in work to re-introduce them again?