@PeterN_UK I rarely block doors as caustic especially if my team is outside. the only time I do it is when we are all in the same building and trying to control the flow of the fight.
Plus I want the enemies in my gas, so I tend to put them next to the doors just enough so they walk into it. I feel like better caustic mains do this. They use the gas in three ways 1. is to cover for revives/healing and 2. they are attempting to get the enemy in it. 3. is to cover flanks and give your team a place to fall back to for healing.
Blocking doors is really camper style play and should only be done when reviving or your team is in serious trouble.