I think your pairing is just fine the way it is for a 3 day split.
I prefer to do a 4 day split:
A: Chest and triceps
B: Back
C: Shoulders and biceps (including traps)
D: Legs
I now do this over 8 days and do cardio on the off days only. I also hit abs on off days about once a week. I've tried this routine over 6 days, 7 days and now 8 days. Perhaps I'm showing my age (49), but 8 days seems about right now.
Looking at my above split you may ask why I don't do biceps with chest instead of triceps (A very good question). The reason is that I like to go into a back workout with fresh biceps. I also find that triceps workouts follow nicely after doing chest.
You may also ask why I have a seperate shoulder day (another good question). I'm currently prioritizing shoulders because years of doing them half-heartedly after chest, or on back day has not yeilded the results I desire, and I desire cannonball delts more than any other single bodypart.
Many of you may think that 8 days between bodyparts is too long. I solve this problem by doing some light back work on chest day and light chest work on back day...mostly inbetween sets. This also serves as a good 'opposite muscle' stetch. Legs are not a problem because they are used extensively during my cardio workouts. Biceps, triceps and shoulders get worked on more than one day so they are never resting too long between workouts.