If the forwards and goalies actually play fine, then the D should most likely be good enough to compete for a playoff spot like we did last year.
The D should also be at worst marginally better thanks to internal upgrades alone.
Positionally, I think we have everything we need up front aside from two second line forwards. Zacha could be one of those, but that remains to be seen.
Defensively, I'd say Vatanen and Severson are both high-end second pairing and low-end first pairing defenders. With the right partner, they can play quality top pairing minutes. They could also hold down a second pairing against lesser competition as well. Neither one is good enough to be on the top pairing with any of our current defenders either.
Greene and Butcher I would say fall into the next category of high-end third pairing but low-end second pairing defenders. They shouldn't be on the top pairing or else they would get exposed. But they can form a quality second pair and a very strong third pair.
The rest of the defenders we have except for the promising ones like Davies and Smith are decent third pairing material at best.
I still think that a top pairing LD would make a worlds difference to our defense pushing everyone into the right roles. Especially one that would pair well with Vatanen or Severson.