[Moto Maxx Android Development] Septfox:
As far as I've seen, hard reboots are caused by kernel panics...unfortunately, "the kernel" encompasses a lot of stuff.

Best way to see if it's related is to grab console-ramoops-0 from /sys/fs/pstore/ after a reboot, and open it in a text editor. Both the ones I posted ended the same way:

[ 661.713308,2] WARNING: at /home/bhb27/android/apq8084/kernel/irq/manage.c:555 irq_set_irq_wake+0xd4/0x108()
[ 661.713320,2] Unbalanced IRQ 432 wake disable
[ 661.713327,2] Modules linked in: wlan(C)
[ 661.713344,2] CPU: 2 PID: 14064 Comm: sh Tainted: G D WC 3.10.105-BHB27-Kernel-V4.6 #1
[ 661.713369,2] [<c010db7c>] (unwind_backtrace+0x0/0xfc) from [<c010ab0c>] (show_stack+0x14/0x20)
[ 661.713388,2] [<c010ab0c>] (show_stack+0x14/0x20) from [<c0169f80>] (warn_slowpath_common+0x60/0x88)
[ 661.713404,2] [<c0169f80>] (warn_slowpath_common+0x60/0x88) from [<c0169fdc>] (warn_slowpath_fmt+0x34/0x4c)
[ 661.713420,2] [<c0169fdc>] (warn_slowpath_fmt+0x34/0x4c) from [<c01e6538>] (irq_set_irq_wake+0xd4/0x108)
[ 661.713439,2] [<c01e6538>] (irq_set_irq_wake+0xd4/0x108) from [<c091360c>] (mdm_disable_irqs+0x78/0x90)
[ 661.713456,2] [<c091360c>] (mdm_disable_irqs+0x78/0x90) from [<c0913818>] (mdm_notify+0x17c/0x330)
[ 661.713473,2] [<c0913818>] (mdm_notify+0x17c/0x330) from [<c013f4f4>] (subsys_panic+0x1c/0x34)
[ 661.713491,2] [<c013f4f4>] (subsys_panic+0x1c/0x34) from [<c054d328>] (bus_for_each_dev+0x70/0xb0)
[ 661.713509,2] [<c054d328>] (bus_for_each_dev+0x70/0xb0) from [<c0140638>] (ssr_panic_handler+0x20/0x34)
[ 661.713528,2] [<c0140638>] (ssr_panic_handler+0x20/0x34) from [<c0baa6bc>] (notifier_call_chain+0x78/0xb0)
[ 661.713545,2] [<c0baa6bc>] (notifier_call_chain+0x78/0xb0) from [<c0baa798>] (atomic_notifier_call_chain+0x3c/0x5c)
[ 661.713562,2] [<c0baa798>] (atomic_notifier_call_chain+0x3c/0x5c) from [<c0ba0030>] (panic+0xc4/0x1f0)
[ 661.713579,2] [<c0ba0030>] (panic+0xc4/0x1f0) from [<c010afac>] (die+0x494/0x4a0)
[ 661.713595,2] [<c010afac>] (die+0x494/0x4a0) from [<c0b9fe28>] (__do_kernel_fault.part.3+0x64/0x74)
[ 661.713611,2] [<c0b9fe28>] (__do_kernel_fault.part.3+0x64/0x74) from [<c0baa364>] (do_page_fault+0x244/0x47c)
[ 661.713627,2] [<c0baa364>] (do_page_fault+0x244/0x47c) from [<c01002a4>] (do_DataAbort+0x44/0x178)
[ 661.713647,2] [<c01002a4>] (do_DataAbort+0x44/0x178) from [<c0ba88d8>] (__dabt_svc+0x38/0x60)
[ 661.713659,2] Exception stack(0xddfa3ea0 to 0xddfa3ee8)
[ 661.713671,2] 3ea0: 00000001 00067200 00000043 00000000 c1462fd8 c12b6810 00000002 00000006
[ 661.713684,2] 3ec0: e5e7aa98 ddfa3f80 e77459cc c12b706c c68628b0 ddfa3ee8 c0186b60 c081f05c
[ 661.713695,2] 3ee0: 20000013 ffffffff
[ 661.713715,2] [<c0ba88d8>] (__dabt_svc+0x38/0x60) from [<c081f05c>] (store_profile_number+0x1d4/0x298c)
[ 661.713738,2] [<c081f05c>] (store_profile_number+0x1d4/0x298c) from [<c02ca1b4>] (sysfs_write_file+0x180/0x1dc)
[ 661.713760,2] [<c02ca1b4>] (sysfs_write_file+0x180/0x1dc) from [<c02674d8>] (vfs_write+0xbc/0x1b0)
[ 661.713776,2] [<c02674d8>] (vfs_write+0xbc/0x1b0) from [<c0267aa0>] (SyS_write+0x48/0x8c)
[ 661.713793,2] [<c0267aa0>] (SyS_write+0x48/0x8c) from [<c01064a0>] (ret_fast_syscall+0x0/0x38)
[ 661.713806,2] ---[ end trace ffb2ce9caf5c56a0 ]---
[ 661.713817,2] ------------[ cut here ]------------
[ 661.713830,2] WARNING: at /home/bhb27/android/apq8084/kernel/irq/manage.c:555 irq_set_irq_wake+0xd4/0x108()
[ 661.713841,2] Unbalanced IRQ 433 wake disable
[ 661.713849,2] Modules linked in: wlan(C)
[ 661.713863,2] CPU: 2 PID: 14064 Comm: sh Tainted: G D WC 3.10.105-BHB27-Kernel-V4.6 #1
[ 661.713881,2] [<c010db7c>] (unwind_backtrace+0x0/0xfc) from [<c010ab0c>] (show_stack+0x14/0x20)
[ 661.713897,2] [<c010ab0c>] (show_stack+0x14/0x20) from [<c0169f80>] (warn_slowpath_common+0x60/0x88)
[ 661.713912,2] [<c0169f80>] (warn_slowpath_common+0x60/0x88) from [<c0169fdc>] (warn_slowpath_fmt+0x34/0x4c)
[ 661.713928,2] [<c0169fdc>] (warn_slowpath_fmt+0x34/0x4c) from [<c01e6538>] (irq_set_irq_wake+0xd4/0x108)
[ 661.713945,2] [<c01e6538>] (irq_set_irq_wake+0xd4/0x108) from [<c09135ec>] (mdm_disable_irqs+0x58/0x90)
[ 661.713959,2] [<c09135ec>] (mdm_disable_irqs+0x58/0x90) from [<c0913818>] (mdm_notify+0x17c/0x330)
[ 661.713975,2] [<c0913818>] (mdm_notify+0x17c/0x330) from [<c013f4f4>] (subsys_panic+0x1c/0x34)
[ 661.713990,2] [<c013f4f4>] (subsys_panic+0x1c/0x34) from [<c054d328>] (bus_for_each_dev+0x70/0xb0)
[ 661.714005,2] [<c054d328>] (bus_for_each_dev+0x70/0xb0) from [<c0140638>] (ssr_panic_handler+0x20/0x34)
[ 661.714021,2] [<c0140638>] (ssr_panic_handler+0x20/0x34) from [<c0baa6bc>] (notifier_call_chain+0x78/0xb0)
[ 661.714037,2] [<c0baa6bc>] (notifier_call_chain+0x78/0xb0) from [<c0baa798>] (atomic_notifier_call_chain+0x3c/0x5c)
[ 661.714052,2] [<c0baa798>] (atomic_notifier_call_chain+0x3c/0x5c) from [<c0ba0030>] (panic+0xc4/0x1f0)
[ 661.714069,2] [<c0ba0030>] (panic+0xc4/0x1f0) from [<c010afac>] (die+0x494/0x4a0)
[ 661.714084,2] [<c010afac>] (die+0x494/0x4a0) from [<c0b9fe28>] (__do_kernel_fault.part.3+0x64/0x74)
[ 661.714100,2] [<c0b9fe28>] (__do_kernel_fault.part.3+0x64/0x74) from [<c0baa364>] (do_page_fault+0x244/0x47c)
[ 661.714115,2] [<c0baa364>] (do_page_fault+0x244/0x47c) from [<c01002a4>] (do_DataAbort+0x44/0x178)
[ 661.714131,2] [<c01002a4>] (do_DataAbort+0x44/0x178) from [<c0ba88d8>] (__dabt_svc+0x38/0x60)
[ 661.714143,2] Exception stack(0xddfa3ea0 to 0xddfa3ee8)
[ 661.714154,2] 3ea0: 00000001 00067200 00000043 00000000 c1462fd8 c12b6810 00000002 00000006
[ 661.714167,2] 3ec0: e5e7aa98 ddfa3f80 e77459cc c12b706c c68628b0 ddfa3ee8 c0186b60 c081f05c
[ 661.714178,2] 3ee0: 20000013 ffffffff
[ 661.714194,2] [<c0ba88d8>] (__dabt_svc+0x38/0x60) from [<c081f05c>] (store_profile_number+0x1d4/0x298c)
[ 661.714212,2] [<c081f05c>] (store_profile_number+0x1d4/0x298c) from [<c02ca1b4>] (sysfs_write_file+0x180/0x1dc)
[ 661.714230,2] [<c02ca1b4>] (sysfs_write_file+0x180/0x1dc) from [<c02674d8>] (vfs_write+0xbc/0x1b0)
[ 661.714246,2] [<c02674d8>] (vfs_write+0xbc/0x1b0) from [<c0267aa0>] (SyS_write+0x48/0x8c)
[ 661.714262,2] [<c0267aa0>] (SyS_write+0x48/0x8c) from [<c01064a0>] (ret_fast_syscall+0x0/0x38)
[ 661.714274,2] ---[ end trace ffb2ce9caf5c56a1 ]---
[ 664.715007,2] ext-mdm qcom,mdm0.74: mdm_notify MDM2AP status did not go low
[ 664.721122,2] Rebooting in 5 seconds..
[ 669.722696,2] Going down for restart now
[ 669.723396,2] Calling SCM to disable SPMI PMIC arbiter

"[ 661.713327,2] Modules linked in: wlan(C)" would seem to suggest that my issue was wlan related.

It seems to have cleared up following a /system wipe and reflash, having successfully idled for a couple hours now, but we'll see. I've disabled Aggressive Doze for the meantime so that the CPU gets woken more; if the problem still exists, hopefully this will cause it to pop again sooner.