Before I start: In fairness, the devs did a lot of what I'm going to talk about in certain places. I just don't think they do it nearly enough.
The Void is a paradox, it's absence made manifest. Its presence on the battlefield should reflect that. Everywhere the Devouring Host marches through should disintegrate into nothingness as the voidspawn are actively absorbing and consuming the very existence of our plane. The Devouring Host should leave nothing but a vacuum of emptiness in their wake. Places the Void strikes should be gone. Not "destroyed", gone! Vanished! No more! The land, the magic, the very souls of the fallen? All of it lost forever. Consumed by Xal'atath's malice.
Show us the scenario that prompted Sargeras to wage his Burning Crusade. Show us what was so horrific to him that it made the heroic titan who once sought to protect the universe from demons decide it would be better to bathe the universe in a cleansing fire using those very same demons and then murder his own siblings when they tried to stop him. Make us feel Sargeras' fear. Make us understand how someone who was once motivated by altruism and a love for life could be driven to sterilize the universe with cruelty on an incomprehensible scale.
I wish we saw void spawn sucking out the souls of defeated enemies. Like in the Intercession cinematic there's a point where a voidwalker pins down a blood elf and for a quarter of a second it looks like its about to eat the blood elf. I really wish it did because that would be terrifying to watch and really give us a feel for how monstrous our foe is.
This raises the stakes because if we lose here and are forced to retreat: There will be no "rebuilding" later because there will be nothing left to rebuild. It also makes it scarier from the characters' perspective because if you die here there is no afterlife for you, your very soul will be consumed. Fighting this foe takes true courage and that's why the Light chose us, it feels our conviction, our drive to save our home being so strong that we'd wager our own existence on it.
Again like I said, the devs did do quite a bit of what I'm talking about. But I wish they hammered it home harder. Like most of the Isle of Quel'danas should have just been disintegrated in that initial attack at the beginning of the expansion, with only the area around Sunwell remaining. Give us a taste of the consequences of failure. We saw it on K'aresh but that was far away and we don't even know what it looked like before. We need to see it on Azeroth. See that same kind of annihilation in a place that we know was once vibrant and beautiful.