Dew,
Pouring water onto the rig may not have accomplished anything but it's probably a bit irresponsible to claim it exacerbated the problem at this point. Early on it looked like the rig was going to sink and the situation was probably one of "damned if i do and damned if i don't". Since there were 11 missing crew I suspect part of the intention for using fireboats was toward recovering bodies. In addition, without any water being sprayed on the ship, the temperature across the rig would've been much higher and that could've also accelerated the sinking (e.g. at some point the ship's fuel tanks would've exploded). Even at the distance taken by the fireboats, the crews of those boats couldn't stand on the side facing the fire for long.
regards,
Charlie