And I thought physics still applied and energy had no mass...
But as an explanation of your quandary, he can "see" smells, and cloaking tech doesn't hide scent. My quandary is a bit more difficult to solve. Not only is there the issue of the energy being treated sort of like solid matter, but also the issue of which person max is aiming that last arrow at. I really hate to come in and start harping on the boss, but I'd be a hypocrite if I didn't.
So, that said, you should probably edit your post Max. According to LeeRoy's undead bio, the soul energy explodes on contact. It doesn't change direction. You should also clarify who you're shooting the last arrow at, because Ozzy and the fire Mage aren't standing together.
EDIT: Also keep in mind that when the soul energy explodes, it's going to create a shotgun blast of smaller soul shards, not detonate like a normal explosive.