I used to have a 2011 F450 with the 4.30. I always thought it was overkill but when I bought my '15 F350 with the 3.55, it was for a TT toy hauler. But now we have the Vengeance at well over 15,000 lbs. and I was seriously concerned about that gearing.
The 3.55 is perfect for us. We have no mountains but typical interstate travel is a breeze for the truck. Getting onto the highways is strong and setting the cruise at 70 mph is no problem and it rarely ever drops out of 6th gear.
Don't worry about the 3.55 at all.