OK, I think there might have been a mix up in your round summary, then.
From the R#1 summary:
DM:
Everyone can see the two skeletons as the party
If this were the case, then Derry could not have killed one skeleton in R#1 and the other in R#2.
Further, we could have lost initiative in R#2, allowing a surviving skeleton the opportunity to attack. That's why I wasn't keen on the hireling idling in R#1.
Just talking this out.