Not necessarily. I had DAL -3 +107 which was superior to any -2.5 line I saw (like you, the best I saw was -117). I also took AZ +3.5 +100 instead of +4 -110. The only +4.5's I saw were on books that no longer take my action and +3.5 +100 is about the same as +4.5 -113, so the line I got was only a little bit worse than the best line I saw. (Of course in the games where I got great lines, MIA +14 and PHI +10, I wasn't even close to needing the extra points.)
I understand the point you're making but with the variety of ways that books shade juice you can't really make blanket statements like "All bettors on team X should have won" when the line lands close to the number. I read a thread on another message board where someone mentioned betting JAX +8 +107, which is superior to +9.5 -110.