Mark VI Interceptor without Leviathan?

If you have all the other sith ships they will be semi useful with Thrawn, maybe.

You could probably throw all the new Sith ships together as a cleanup fleet at the very least.

But depending on how far you actually are from Leviathan reqs, you may not want to spend crystals on the chase. It will become farmable at some point. No one can be sure right now if the new ships could be some amzing off-meta counter without the cap. But your post is kind of vague about where exactly you are in your roster.

Just found your swgoh.gg. For you, I definitely wouldn't waste resources on the galactic chase. This ship won't help you. Just continue to follow regular farming guides for both fleets and squads.