You might find that the difference between Load D and E is the tread ply rating, not the side wall. Most load D have a 3 ply sidewall and 8 ply tread, although some will have a 2 ply sidewall, where Load E tyres will generally have a 3 ply rating on the sidewall and 10 ply rating on the tread. I do not know if the E 3 ply is stronger than the D 3 ply though.
Some of the older BFG's are also C rated but have the Triguard 3 ply sidewall and only a 6 ply tread.

 

The only thing you can count on for E's is that they're rated for 80 PSI. The rest that's relevant as far as load is in the Service Description numbers. Useful comments on sidewall strength in off road situations are best gathered from your friends and trusted Internet sources. Actual number of plies and ply ratings are largely obsolete indicators and can be misleading.

Just my opinion.