its ok to train your traps with your back. because some of the trap exercises have the same basic movement as the back (secondary muscles being the bis especially doing upright rows etc.)
Do delts on a separate day or work them on chest day. because they have the same basic movements as the chest (a pressing movement. hits the tris as a secondary.)
If you hit your chest hard and good enough one day should be good enough. if your chest isnt growing well you may just not be hitting it well enough. Have you been at this lifting for a while or are you just starting out? If youve been after it a while do atleast 4 different exercises with atleast 4 to 5 sets each.
I personally would hit them for 4 exercises minimum and a minimum of 4 sets each.
I workout different then most that I have read about. I have had great gains so I dont plan to change for a while.
When doing sets I do 2 light and 2 heavy. The light I hit hard enough to put a burn in the muscle at 10-12 reps(but could still do 14 if i tried). On the heavy I do 6-8 reps to or near failure. Each rep I do slow to moderate speed and exaggerate at the top of the movement. Each set I pause for 4-5 minutes rest.
I do the 2 light to hit the slow twitch muscle fibers and the heavy for the fast twitch. I have never had as good a workout until I started this. Its a beautiful workout man! Let me tell ya!
At the end of my workout I do a burn set. I start with a moderately heavy weight and do 14 to 16 reps. Then non-stop, no breather, I lighten the weight one plate or a few pounds lighter and burn for the same 14-16 reps. I continue this for about 5-6 reps or until I cant do no more. Until my muscles are ready to detach and say "I quit! Im outta here!"
When I planned my split I made sure that my basics and secondaries got atleast one day off before hitting them again. Except sat and sun. These are my major recoup days. (plus my wife and I are off on sats and suns so I spend the time with her)
This is my split (yes I know that there are some that dont agree but it works for me. which that is the key to you find your own workout. what works for you works for you. it may not work for anyone else. it takes time and experimentation.)
Monday: Tris and Bis
Tuesday: Legs
Wednesday: Delts and Forearms
Thursday: Back and Traps
Friday: Chest
Saturday: Off
Sunday: Off
This workout I have had, like I said, the best gains so far. On arms I have almost broke 17" (not that much of an accomplishment for most but it is for me). I have been getting compliments now also. Good indication something is working.
Good Luck!
