Arms

Does a person with good arm strength/development need to train arms if they are after increases in functional strength not necaserily hypertrophy(although it is not unwanted)
What percentage of time should be spent on arms?
Since close grip bench presses and other compound arm movements also work core muscle should they be counted as a fuctional exercise that happens to work arms or an arm exercise that also is functional
Are they worth doing? or should I stick to bench and dips etc
ive decided to do virtually no isolation work for arms
is that wise?