I have a question : How much trouble would one of us have in fighting a fleshnid? AKA, am I allowed to 'auto-hit' and potentially 'auto-kill' one or two of them while fending off a couple others? 

Can I : "The blade swung in an arc, slicing through the abdomen of the creature"  

OR   "The blade swung in an arc, intending to slice through the monster" and then wait on the GM post to determine if my hit was successful and if it did anything? I imagine this would be case when fighting something big and scary like a boss, but does it also apply for the 'mobs'?