Every year there is an unknown goalie playing lights out (usually for a team *other* than the Senators). Many teams managed to make it far in the playoffs without a Shesterkin, Hellebuyck, Vasilevskiy and so on. Similarly every year we see a goalie who played lights out the previous season regress (and it's not necessarily the "unknown" goalie from the previous season). Overall SV% in the NHL is declining. All that to say that it's not so much the goalie as it is the circumstances. In Forsberg's case he was never advertised as a #1, and if he's only playing 20-25 games I think he'd be fine. As for Korpisalo I just don't know -- some nights he's very good, other nights he stinks. Is it a confidence issue (confidence in himself as well as in his defense)? If he doesn't trust the D to take care of the slot pass he could end up cheating to the far side and give up a bad goal on the short side. I don't have the stats to confirm or deny, but this is a goalie capable of consistently making 9 saves on 10 shots.
Moving out from goal, we need to balance at least the top four. It's one thing when your #5/6 is playing his off-side but a top-4 playing 25+ minutes on the wrong side is not ideal. We also need to have some balance in the stay-at-home vs. puck-mover department. Chychrun has the tools to be a tough, crease-clearing D-man but for some reason he doesn't do that. You'd think a guy who eats raw liver would be a lot sturdier back there. At the same time he's a leftie. I think he will be moved.
I like Brannstrom but he's another leftie and is not blessed with size. I see him being moved somewhere. Personally I wouldn't mind trying him out as a winger for a stretch.
The bottom 6 needs an overhaul. Kastelic, Kelly, Kubalik -- three strikes and you're out. I would prefer Katchouk over all of these, and I wouldn't bat an eyelash of he was moved. The top six is fine if you ask me, but Norris' third shoulder surgery is very troubling. If Norris is healthy and Greig/Joseph are playing on the third line like they should be that would certainly help.