The issue comes from giving an option for people who want to catchup a way to do the new content without needing all the gear. Pretty much if you play regularly the new dungeons are going to be easy because you could say the dungeons are 1 patch behind on the best gear from the patch before.
Let's look at current gear, started around 220, have 230 by 3.3 and then 240 by 3.4. So 3.2 was 180 and 3.3 200 but see by 3.3 you are nearly at 230 if you gained tomes regularly so it's just going to be easier for you. It's a 200 dungeon, that drops 215 gear so already you can tell that these dungeons aren't designed for players like us that are already past that IL. If they made the content harder then people who would be using those dungeons to obtain il 215 gear if say they only have i200 esoteric set wouldn't be able to get the gear because it would be to hard for the reward.
Dungeons are nothing more than a means to gear up a tad faster while gaining tomes and replacing gear as needed or for glamour. It's hard to adjust dungeons to be harder because if you get the difficulty to obtain gear from that content closer to the cost/time of obtaining tomes you negate the usefulness of said content for people playing catchup.