For an all-day affair, you certainly have what would seem to be the right amount of gear, nothing extraneous. I carry about the same thing. The belay mittens and parka depend on the conditions and everyone is different. Since this amount of kit isn't really a burden weight-wise the only problem you may be encountering is time.
If you arrive at the belay, tie into the power point, pass the pro to the leader, and then put on your jacket and mittens before putting the leader on belay you are probably wasting a little time that you could save.
After you tie in and pass the pro, clip your pack into the belay gear. Set the leader on an auto-block so he can begin moving out and only then begin to satisfy the clothing, food, water issues. The leader is now on belay and you are simply minding the rope, feeding slack, and tracking his/her progress. Your hands are mostly free to take care of your needs at the belay.
If you give this a swing next time you're out you may just find it helpful.
Ken