I don't think my ride is harsh at all on E's. I have Toyo R/T Trails in 295/70R18 and I came from smaller P Toyo ATII's on 20's. 35psi is what is recommended, but I run it a little higher than that. It is a little noisier than the ATII's because they are R/T's but it doesn't bother me.
The vast majority of 18" AT tires are E-rated. I ran them, they were OK. I moved to a 17" D rated tire in a wider size and the ride quality improved significantly with no hit to handling. The load rating is still more than adequate for my towing needs. So far they've been durable in off-road use.
E tires are tough. My old E-rated hankooks had a 1/2" deep, thumb-sized chunk of rubber ripped out of the sidewall and I just rubber cemented the chunk back in place and kept running the tire, even aired down off road, for quite some time. Didn't even make it down to the internal structures---lots of rubber thickness. I eventually replaced for peace of mind, but never had a problem.
And I'd say that's a big "maybe." Even those LT-C's need a good bit more pressure than the ISO or P-metric option and that's a big part of the ride quality difference.