Indeed a tragic event, but I know only too well how difficult it is
To spot traffic, even with a TCAS system displaying position and altitude information and with 3 pilots in the flight deck.
While I don't know the specifics of this event, I know helicopters can be extremely difficult to see at the best of times. It's not as easy as "just use airmanship and look out the window and you"ll see them"
As previously mentioned the aircraft still has to be operated and while a visual lookout is extremely important, it can't be done 100% of the time. Communication is a big one here and i'd be willing to bet this is a factor in this accident.