Ya I agree on Mirage/Toxic needing buffs
1) His ult and decoys might work better if the decoys fired weapons/made it hard to tell it was a fake (the firing weapons does no damage, of course). Kind of like Total Recall "Ha ha ha, you think this is the real Quaid? It is *BRRTTTTT*". If they made that change, it would differentiate him a lot more from Wraith and make him a much more viable pick.
2) Toxic's gas doesn't do enough damage or debuff enough to act as a deterrent. Unless a player has no HP or is trapped in a tiny room, it's low risk to rush the gas and take out the Toxic or whatever else. If they buffed the potency of the gas, either to do more damage or disorient you more, it would e more effective. Maybe also apply a debuff so Toxic can see the players for a period of time after they leave the gas cloud, making its tactical use much better (esp for the proximity mine cannisters).