I have had several sets of Toyo AT2 in 265/70-17, 285/70-17, 285/75-17 and 35/12.5-17 in E load and just put on a set of AT3 in C load ie 35/11.5-17 and being I only put them on Tuesday I have only put about 150 miles on them my first impression is they are loud. they replaced a set of ST Maxx in 315/70-17 D and they are louder than those and I also run a set of Falken at3w in 255/80-17 E and they are louder than those as well. I am hoping with a few more miles they quiet down but that has not been my experience in the past.E-rated is referring to being a tire constructed for 80 PSI maximum pressure; which is considered 10-ply rated. Being that we're talking radials and not bias ply tires, the archaic ply lingo is a bit strange, but that's what the tire industry has held on to.
General tire info: If you take a given tire size (lets say, LT265/75R16 and compare a C rated (max press. 50 psi, 2470 lb max) to a D rated (max press. 65 psi, 3000 lb max) to an E rated version of that tire, the E rated tire will be rated for more weight (3415 lb max) at its maximum pressure. Keep in mind, at a given pressure (e.g., 50 psi), they all are rated for the same weight. In this case that's 2470 pounds. The higher load capacity of the E-rated tire is because an E-rated tire is capable of handling the higher inflation pressure required to bare that higher weight. In order to be able to handle those higher pressures, E-rated tires tend to have more rugged construction, which incidentally enhances off road durability at some sacrifice to tire flexibility and total weight. How much more durable, I don't know? I find the load inflation tables useful, here is Toyo's: https://www.toyotires.com/media/2125/application_of_load_inflation_tables_20170203.pdf
They're great tires, but not perfect. They sucked in mud and they're not so cheap these days. I got the new Toyo's for less, as there was a sale. Falken's were a bargain when I bought them, but with a Toyo being cheaper, looking to be better in mud (greater void space), and having a 3 ply sidewall (Falken was only 2 ply sidewall) it was an easy choice. Plus, I'm always looking for the next best tire.
From what I can tell, the AT3 is an improvement on the AT2. May be one to watch going ahead.