If you have everything laid out in front of you, I think it is actually more efficient to call. That way, if there are any hiccups midway through... say you book your first three days of stuff, then want an HDDR reservation for your 4th night, only to find out that HDDR is closed for refurbishment starting the day before. It is easier for the CM to book you into HDDR for one of your first nights, then rebook your earlier reservation that had to be cancelled to the 4th night, or whenever, than for you to book HDDR for one of the first nights online, then get prompted to cancel your existing reservation, then go back and find a time for that ADR later in your trip.
The CMs can also let you know what's going on... say you were booking the above ADRs and could not find any availability for HDDR later in your trip. You might think it was all booked up, but in reality, the venue was closing down. A CM can tell you this, or (like earlier this year) that HDDR had not released dates to the booking system until after the 180-day mark had passed.