Rage Generation for Bowzerkers? Chainbreak or Warlord Mark?

Would that hidden Chianbreaker keystone be my only option to generation rage on a zerker using a bow? I read about it not long ago but my understand is that you'd need an insane amount of mana regen % to stop yourself from losing rage on attack.

I know people use the keystone for passive totem play so they can start the boss fight at max rage then pop Berserk. That's boring to me and I like attacking. Mapping is great a few seconds or so after starting but boss fights are a pain.

The 20/rage on stun for Warlord's Mark is a bit confusing because I don't fully understand how stuns work, esp when it comes to elemental dmg types. I'm currently using Flammability curse. I'm not sure if there are stun cooldown windows before you can even stun again on a boss?

Right now I'm playing Explosive Arrow so I assume a big explosion = higher chance to stun compared to individual attacks? I'm still not 100% certain if all my extra atk dmg is being added into the explosion but the speed is nice to stack arrows quick.