At first I was thinking it could be different road surfaces but I see that we live around the same general area and we are pretty much on the same road surfaces.
It's been raining on and off all day here and I spent the better part of the morning all over the Baltimore beltway with no issues.
There are the usual slick spots in the rain like left turns at intersections or tightly turning highway on-ramps but I haven't found the tires to be less confidence inspiring than my previous, stock sized and rated, Nitto Terra Grappler.
I have my 285/70/17 Load C inflated to 40psi though.
Maybe you have yours up too high?
I know sidewall says 50psi for the C rated but that may be too high for normal street driving and the weight of our 4Runners.