Has anyone tried killing both the hunters and Sindling?

I have. You get both rewards. It might have gotten patched though.

sigh

Yeah, I have fun. I guess it's just become a (minor) pet peeve of mine that too many people's entire consciousness of folklore only consists of things that were created in maybe the past ten years, the past fifteen tops. I'll take a wild guess and assume that the OP is almost certainly under 30, and there's probably a greater than 50% chance that he's not yet old enough to have graduated college. Nothing wrong with that; everybody was under 30 for a period of time - for the first thirty years of their life, to be exact.

But werewolves and vampires did exist in fiction prior to the debut of Underworld and Buffy the Vampire Slayer, I promise you. Yesterday I mentioned - I think it was yesterday, my aged brain is getting foggy and the days of the week just blur together here in the old folks' home - I mentioned something about vampires not being able to cross running water, and one responder had never heard of such a thing. It's an old part of vampire folklore, along with garlic, holy water, crosses, not being able to enter homes uninvited, stakes through the heart, sunlight being deadly, and so forth. Werewolves change involuntarily with the full moon, can be killed with a silver bullet, and have an uncontrollable urge to kill.

None of this means that Bethesda is obliged to employ all the ages-old details of the folklore, of course. This isn't about how the developers work out their version of lycanthropy and vampirism. My point is just that young people seem oddly unaware of very much beyond maybe fifteen years ago. Werewolves are Lycans, because Underworld called them Lycans. Vampires have a "human form" and a "vampire form" and the vampire form has a bumpy forehead, because that's how Buffy portrayed them.

Fads will be the death of us all.