One of the limitations of Logic‘s automation system is that there is no way to increase or reduce all automation data at once. Consider a typical mixing scenario: you’ve adjusted all your backing tracks until you’re happy with the mix, but you need a few extra decibels on vocals and bass drum. However, just raising the levels of these tracks takes the mains over 0dB. What you really want to do is lower all the other tracks proportionally instead. To do this, you’ll have to lower the volume and, perhaps, other automation data on each track! Imagine how long this would take if you had 48 tracks with complex automation of multiple parameters!
Although there are various automation-editing commands that can help to make this easier, you may also want to think of mixing using the stem technique. What this means in practice is sending several similar tracks to busses as “stems.” For example, you might send all the drums to one bus, backing vocals to another, guitars to another, and so on. Balancing then becomes just a matter of adjusting the levels of the stem busses rather than those of all the individual tracks — and you can automate these busses too. Stems can also be compressed individually, which can help in getting things to ‘sit in the mix’. Of course, you will still have to edit other automation data, such as a synthesizers’ filter cutoff, individually for each track — but it’s unlikely you’ll need to do this simultaneously on many instruments.