Are bicep workouts unnecessary if you do heavy back workouts (deadlifts, rows, pull downs, chin ups/pull ups)?
deadlifts doesn't work the biceps at all, it's also very stupid to even want to try to incorporate your biceps for deadlifts. a lot of lifters thinks it helps by bending their arms trying to use their biceps to help during the lock out and that's how people tear their biceps. during deadlifts you want to engage your triceps by locking out your elbows and pointing them to the wall behind you and activating your lats, rather than your using your biceps. main movers for deadlifts starts with your legs and then becomes a back exercise during lockouts. when deadlifts are done right, there should be 0% of bicep involvement.
rows, lat pull downs, and pull ups, you're mostly using your lats and upper back to do most of the work, placing minimal effort for biceps at the end of each rep.
chin ups uses more biceps, but the main movers are still the back.