Raner just doesn't see a good reason to pick a fight with armed, aware individuals when the rest of the party isn't much further away than around the corner.
The gnolls are not sufficiently trivial opponents that Raner feels he can take two of them by himself, especially when he's already wounded. The odds of winning the fight with no significant injuries/deaths on our side go way up if we round up anyone else first.
Raner's seen two people die in the last 24 hours. He's not anxious to join them.
(What? A PC with a resonable sense of self-preservation? I'm not sure that's ever happened before... )
Raner is probably acting like the prudent business person he is.
Kerwyn is a rogue, so he probably figures that if only two people split the loot, there is more for each of the two (assuming 1 pc dies in a 3 on 3 fight).
Well, a crossbow shot right away would be a more approriate approach, since we (Kerwyn's idea, my scepticism says she's a high-level cleric with a good Con with a plate-mail under those robes) can take out one cultist in a flurry, and then focus on getting the gnolls.
Kerwyn isn't exactly the one with lots of common sense. See, he's remained unscathed so far, and he managed to fool master wizards for a while, so he's got a bit too much confidence. At least he didn't just walk in and challenge them to a game of poker like he first thought