I couldn't figure out how to get the bone armor stack to stay at 15 when there is never more than 8 mobs at one place at a time. Without full stack, I would get one shotted at GR. Certainly, I can TP to another waypoint to get all the stacks, but it is a chore to do so every minute. Is there a better way to keep the bone armor stack at high GR?

I didn't get your post until I read "it is a chore to do so every minute". Welcome to diablo 3 where each buff lasts 5 seconds. Yeah I don't like it either so I usually put a macro to spam my skills. That includes bone armor. 95% of the time is up if you keep moving your ass.

My macros are on the mouse, logitech (strongly suggest you don't use their scumbag company though).

Also maybe you got low cooldown and low movement speed.

guides on maxroll.gg for necro