Patch Broke Karma Boosters
Last game they made they kitten up skill balancing and accidentaly created an entire new play style (solo-farming + speedclears). Once GW2 came close to fruitition they completely destroyed (“fixed”) it so they people would get used to being screwed over by the time GW2 dropped. My advice is take a week/month break and come back to see how it’s doing then.
Karma boosters work fine. The medallion / popup does not reflect the total incoming karma including boost, just the standard event karma.
Look at your karma in your bag window before and after an event with a boost activated, you get the full amount.