At beginning I would like to express my understanding of "Demon" part of this story...
My meaning is that every personality have part what is drained by fears , bad memories, childhood traumas, hidden secrets or another type of "demons" , where the scariest one is EGO...

HUNTERS

1. Like in story Illidan need to take demon hunters outside of this world to beat enemy there... ( You can't fight with your demons in public... you need to come to their world and beat them up there... That is symbolism that battle what you fight is inside you no in your partner, work , parents etc... and if you won on their own place ... They start fear you... like your EGO will fear you if you show no mercy to come for that cunt inside and kill him before he slowly poison your life with worries).

THEY and US

2. " What is the difference between us and them if in our vein is theirs blood " Just when you fall deep to darkness of your own weakness... Then you can truly recognize same sickness in others... Every fear, hate and envy what we successfully kill in us we can recognize in others and lead them to fight their own arena skilled of experiences our own battles...
"They will stopped nothing to destroy our world"
Our fears and nightmares have no home, have no hope, have nothing to lose... That's why nothing stopped them... Those demons will waiting for you in every corner, they will hiding and strike you with your own ideas , struggling and thoughts and will never stop until you decide to rise to fight against...

TRIBUTE or GIFT

3. "We will SACRIFICE everything to protect our world"
"Your world" is your personal peace and mental stability... If you want to heal your SACRIFICE shouldn't be find a doctor... Your SACRIFICE have to be your pain during finding a cure.... ( Symbolism )
And where is the difference? If you feel pain of killing part of yourself during some process of self grow and you are to strong to enough to find a root of problem somewhere in your past not in your partner, enemy or basically outside of your own character... The Lesson of gone thru this hell can be more sweeter than revenge... That hard time can kill that part of demon but most important is that now you have power to see the same demons in other and more than that... You can heal them with your knowledge of that environment and your painfully dark moments turn into light beams for others...