Tier 5 doesn't give you a blanket resistance to all damage, if anything, tier 5 usually includes heightened hearing and therefore more adverse effects from loud noises.

But that's besides the point, it would be difficult if not impossible to hear my characters approach at up to -five- seconds after an explosion goes off relatively close by. It would also be very difficult to see him, due to debris and his cloaking.

None of these things are impossible, but I'd expect to see a serious delay in your reaction time, rather than an acknowledgement, thought process, most tactical combat decision. Its customary to defend against an attack like mine with a reflex move, which is perfectly understandable provided your character has superhuman reflexes, if not, then he's essentially avoiding a spider running at about the speed of a car on the motorway after an explosion blew up in his face, difficult by any means.