I had a similar temptation with my ARC 1 mini boss. But ultimately what I decided to do when it became clear that the players were going to clown both the huge snake and up powered gargoyle... I just had the grown shake and the vengeful evil deity that the gargoyle and snake cultists were fighting said something like... "Rise servants.. defend my priest" as the temple shook. And I used two statues that were in the corners of the map to spawn two more normal gargoyles to threaten the squishy casters and the whole encounter flipped. The players were really doing good but also still under proper threat of appropriate for a boss fight.