Varnias Tybalt I do agree that you should allow (RAW) a reaction dodge to a flamer attack (if all the circumstances for dodge reaction attack & dodging area of effect attacks are met) in addition to the initial AGL test. [Just re-read the rules to get it straight in my head]
However when I have two PCs mass flaming a dozen or so heretics a round it is easier to condense it to one roll.
However my main issue with the RAW is that the flame "to hit roll" is based upon a characters ability to get out of the way of it as specified by an agility roll & I personally believe that dodge skill should come into it in some way (other than as a reaction test if they fail the first test).