It’s quite simple:
Pendles is immune to reveal while Miasma is active.
This way, if the map is littered with a bunch of stuff that reveals–owls, or sunspots, whatever–Pendles no longer suffers such a drastic reduction in usefulness. The Miasma cloud would still reveal his position, sure, but he would retain the Corner Sneak buffs.
I think this would add a new skillful layer of play to Pendles. One would have to play cautiously until level 5, then be faced with a variety of new combat options against heroes with Reveal enabled. Do I hold Miasma in case I’m suddenly revealed, as an escape option? Do I find the stuff that’s revealing me, and try to quickly take it out with Miasma’s DoT? Do I use Miasma to quickly find and finish the hero with the Reveal augment, hoping to kill them and so I can move freely around the map during their respawn timer? Do I cast Miasma to sprint past a choke point, avoiding any CC when they spot me, then try to hide in enemy territory until I’m ready for a flanking attack?
It would also fit with the nature of the skill, implying that the poison cloud was obscuring Pendles enough to negate Reveal. Maybe there’s microscopic countermeasures in the cloud, sort of like Alani’s “magical” nanomachines.
Of all the balance changes I’d like to see happen to the game, I’d say this is now number one on my wish list, even if it came with a nerf in other areas, such as damage.