I'm a River Rescue instructor and have been teaching classes for 11 years. I still try to keep my kits simple though. here is what i bring
for a full expedition run:
5 non locking biners
1 or 2 locking biners
2 12' lengths of 1" tubular webbing, 1 tied into a loop and one at full length
3 or 4 prussik loops
folding knife in pocket, not in sheath. seen too many people roll up to a missing knife.
two throw ropes. one 60 footer around the waist, and one 75 footer in boat.
other safety gear:
goretex patches for drysuits
bitchathane tape for boat repair
extra bolts and parts for kayak
simple first aid kit - gauze, super glue, gorilla tape, lighters, fire starting sticks, ibuprofen, iodine
spare paddle (1 for every two paddlers)