I think sisters of battle are very competitive right now. Their acts of faith this edition are very strong. If you already have a sisters army, you might want to consider using them. Celestine is also a beast.
+1 to this. Sisters right now look pretty decent. A damned sight better than Primaris, at least.
... They operate best in rapid fire range of their weapons (so 15" and closer).
This is true and also the primary *problem* with getting Primaris to work on their own. They work best in rapid fire range, but they have no access to Rhinos, Drop Pods, or Razorbacks. Their only ride is the Repulsor, which is prohibitively expensive.
So you wind up with a bunch of guys who need to get into rapid fire range to get good, but can't actually do that without walking.
Yeah, Hellblasters can wreck vehicles if they get in close, but you can kit out squad of Company Vets with all plasma guns for fewer points and stick them in a drop pod to boot and get more or less the same effect. The Hellblasters have more wounds, but the Company Vets *can actually get into rapid fire range reliably.*
I dig the Primaris models, yeah, but so far the rules haven't backed them up. Regular marines might be a little softer, but they're better at their jobs. Tacs over Intercessors, Assaults/Vanguard over Reivers/Inceptors, and Devs over Hellblasters.