Griffin shows up in Caira's story, which would make her the fifth hired.
As stated above, the dropship the hunters use is the Laurie-Anne, a non-FTL capable TJ-F tug. The larger ship was Nordita EET-105, a medium sized transport ship that brought the Laurie-Anne to Shear and left with the colonists to St. George's World. The dilemma of the hunters on Shear is finding a FTL drive and fitting it to the Laurie-Anne, as stated in the Lennox/Caira/Maggie/Sunny convo.
Rogue Val's outfit is her CIG9 operations suit, which implies that it's Hub.
Where did they say they returned to Shear for this?
Finally found that quote, the hunters do go all the way through and hit the monsters where they live, not just nuke Patterson space. The "back to the Dark Ages" wasn't directly related to that, just the result of a years long war where the enemy focuses on razing all your advanced tech.
Besides my usual points of discourse, this is a good compilation of the timeline. If you're going for completion, you might want to add the events of the Akhenaten story. It doesn't directly feature the hunters but it is the period where the Patterson tech/Monster connection was discovered, which was more than likely the cause of the Extinction attack.