Hi ya Chris
I pretty much fish with riggers. just started to use a diver but nothing yet.
Ok, how far behind the ball are you lures? The watchword of late has been "get them away from the boat". with riggers i go will long leads. i use mostly spoons and above 50' i have them back 125' behind the ball. I shorten that as i go deeper. but not less then 75'
Second. your line. are ya using a invisible type line? fluorocarbon type? that made a big difference with me.
Next I would have to say speed. Run the lure along the side to make sure it has the right action.
Have ya got a graph? if so watch it to see where the fish are located in the water column, not forgetting to let out extra cable.
Lastly, some times it just bum luck. I have a friend that has far better equipment them me, has taught me how to fish the big lake and for the last 2 days has only caught 2 fish. Some times they are not biting.
Good luck, keep trying! Hopefully someone with more wisdom then me will add/correct what I have said.
Mark, Buckshot.