Mari

yeh the Hydra does bugger all damage

It all boils down to gear and self management, though it is solely for you decide whether or not you should risk your life. Unless you feel you have a comfortable assessment on technique and situational awareness, then you should not be taking such heavy risks.

Rue, in this case, should have been prepared with regenerative potions, considering a perfect could heal her for 6HP each post for three posts. Not only does it heavily outweigh the damage the hydra does, but it also doesn't heal instantaneously, which would be a waste for Rue since it heals 15HP. She wouldn't be too safe waiting to use it until 4HP so the potion is a safe bet, but it's too late for her to do so now. Will she rue her participation? Let's see...