Well, gravity pull was not removed from your dragon. Gravity Pull status works like a stack of books. Your dragon was given the status, then your brimstone eater got the status, and was put on top of the stack. The first creature to be hit will be the brimstone eater. When it dies, the next creature on top of the stack will be hit: your dragon. There are ways to manipulate the stack that make things much more complicated (Parallel Universe, Mutate, Reverse Time, Armagio, Gravity Pull card). I will probably write an article on it soon, but to answer your question, no. The AI doesn't take into account whether there is already a larger threat with Gravity Pull status before it applies it again.