At least that is about what I had in my early game chapters and I had 4 maxed armories. This means if you go to sleep for 8 hours your barracks will be idle for 5 hours. Once I got DB my troop situation improved **SO** much. My training time increased dramatically and my military buildings had much less downtime between my log-ins.
Yes, I agree that idle time in barracks is not ideal, and I dislike that as well in early chapters, but in this case, OP is only Chapter 3 and asking for advice. I am only structuring my answer according to their need. Until they unlock DB, Needles on its own will have to do.