At this point I'm pretty happy with our defense provided they are healthy. A group of six of Rielly, Gio, Brodie, Holl, Sandin and Liljegren have shown they can handle tough matchups, and provide a very balanced group. Now we have Timmins as well who can produce offensively, and is a right shot d-man with some size and isn't afraid to use his body either. Then there's Benn as the quintessential blue collar guy who will do the dirty work. Overall, a pretty deep group that I don't think needs any 'fixing'. They do lack some offense outside of Rielly, but Timmins is a dark horse in that regard while Sandin and Liljegren are still developing and have shown glimpses of decent production and skills before.
Definitely to your point, the bottom six needs more. I like Kampf and Holmberg for how they tilt the ice defensively but the rest just don't contribute enough or grind it out when it counts. Anderson is yet to be determined though I like what I see so far from him, but I still want to add a legitimate depth scoring guy built for playoff hockey. We also badly need a true 2nd line LW, and by virtue of acquiring one you automatically make the bottom six better as well because someone like Jarnkrok no longer has to move up the lineup to be a stopgap.