Since Mirage casts his decoys in a perfect circle, it would be easy for enemies to spot the true mirage if you immediately start reviving your ally after casting the ultimate. I suggest after casting the Ult, you should ran around and let the decoys spread and shuffle all around, making enemy see decoys doing reviving everywhere, while the decoys distracts enemies from discovering the dim blue light emitted from the cloaked Mirage's arms.
I personally thinks Mirage's tactical has the least threat in fight, which makes him obsolete in serious fighting. His tactical won't bring hardly any tactical advantage in a close fight beside blocking one punch from the enemy (yes it does take punch damages, but Apex is not a Kunfu game) . Most legends' tactical will pose tactical threat for enemies, or brings advantage to the team or themselves. Mirage's tactical poses nearly no threat, nor any tactical advantage because it is usually easily identified by experienced players. Let alone, the decoys easily gets stuck or even "killed" when sent to places, rendering the tactical's usability even worse.