... what?

If you look at the sum total of rewards from DTH, there is absolutely no comparison at all. DTH is much, much better than normal. I suppose it's possible that the gems specifically may be lower, but why would you only look at that?

This ture but u will think on the gem part will be way more because u need silver to change gear ect on some floors more gems will make more sence lol

Once you get the hang of Doom Tower, you'll be able to do both Normal and Hard every rotation, and can get all the rewards from both! Took at while, but there are so many resources grinding out both Towers.

The usefulness able to farm Hard Doom Tower Bosses for 5-6* gear (especially with some of the more high value sets) cannot be understated. 

The difference in rewards is large too, 50% more energy, over 100% more gems, 2 lego books, 2 sacreds when you finish Hard DT, 2 more voids. 

I hear ya im farm there all the time just was looking at the floors on both and just seemed like on every floor normal was gems hard not so much at least not on this rotation )