Dabi has already sent an AoE in hundreds of meters to set a forest on fire and didn't seem to be very affected by it. In the context of this fight, Dabi will know he is fighting someone, so he can 1) approach the person to launch an attack and 2) immediately launch an AoE to burn whoever it is without the need to move. Which do you think is the more rational thought?
There is a fine line between being OoC and being dumb.
Agreed.
Tbh the problem is not the explosion itself, but the temperature, since Gyomei has never faced such a hot temperature. He could be instantly severely burned just by getting close.