[(Spoilers) Dark side JK: Bengel didn't give me anything!]

He promised me gifts so I let him live (I'm a shallow Jedi) but I got nothing. In fairness, I wasn't 100% clear if he was referring to physical items or metaphorical gifts.

 

I opened a ticket to ask and got a "Thanks for the report, we'll investigate" response.

[Catalyst quest on Taris?(possible spoilers?)]

I spent around 40 mins fighting every Rakghoul I could find and didn't get infected. Following the advice above I abandoned the quest and picked it up again. After that I got infected on the first pull, consisting of standard enemies only.