I agree. Walks shouldn't be a stand-alone category... they're useful when considered alongside batting average in OBP, but they don't tell you that much in isolation. You want your hitter to do two things: (1) get on base; (2) get extra bases. If they accomplish #1 by hitting .400 with 0 walks, that's great. If they accomplish #1 by hitting .000 but walking 4 out of every 10 at-bats, that's fine, too... although they won't be move along any runners.
How about adding Quality Starts instead of your K/BB or BB stat? That would give you:
W, Q/S, SV, HD, K, ERA, WHIP
Wins - Starter advantage; some MRs will hit 5-8 during the season
Q/S - All starters
SV - All closers
HD - All MRs
K - Starter-friendly, ok with relievers
ERA - Reliever friendly, stud starter ok, other starters unfriendly
WHIP - Same as ERA
Relievers would have the edge in 4 of the 7 categories; starters would have the edge in 3. It would force a balanced team without having to worry about streamers or reliever-only guys.
The way to think about categories you're making isn't, "Is this a good category" but rather, "How does this category fit with everything else; am I creating a situation where someone could win by playing a strategy instead of playing good players" because there's plenty of categories that are good that, in combination, create bad situations.
0-3 to 4-3. Worst choke in the history of baseball. Enough said.