I mean there is absolutely zero question that your #1 priority right now needs to be CB. You should be aiming for a minimum of the top chest on Nightmare CB. With that in mind, I would expect your ideal team will be something like:
With that in mind, I'd probably aim for getting Fatman to 60 next, followed by Steelskull.
Eventually though, you will 100% want to build a team centered around Seeker + Ma'Shalled. The team is typically called Bat Eater: https://deadwoodjedi.com/speed-tunes/bateater Until you get those pieces, you'll want to build this one: https://deadwoodjedi.com/speed-tunes/mashalled-white-whale . I'm not recommending those yet simply because they're quite advanced, but you should work towards them.