But the pinion angle is a good bet these days. More and more experience this issue with the newer, thicker spring packs. Even with 2.5" sometimes.
Most of the time it's not until you get to the 3.5 and higher ranges, but anything can happen anytime, so it's worth checking out.
And if your 8° is measured at the rear pinion in relation to the centerline of the driveshaft, then it's definitely too much. Should be between -2° and 0° down, but somewhere in the 1 to 2 degree downbubble seems to work for most.
Shims should fix it, but if I'm not mistaken you usually get more change at the pinion than at the shim. So an 8 degree correction might only need a 5 degree shim. Or something like that. Others will know for sure.
So best to verify your readings (measure twice) before sourcing the shims (cut once) so you don't have to fiddle with it too much.
But like az said too, it's a good time to check the overall condition of the shaft and to definitely lube all 5 fittings, especially if it's been awhile.
Paul
