Click on rewards on the stage selection screen, you will see what drops from each level.  And yes, legendary only from hard DT.

It's a bit silly, to be honest. By the time you can reliably farm legendary material from DT, you'll probably not really need most of it.

Hard disagree. Obviously it can be set dependent but for example, the Fatal set that's mentioned in this thread can be quite useful, not to mention shots at 6* gear even as one off pieces can always be helpful. 

DThorne - I think where EGD is going with this and I tend to agree is we need gear to be able to handle the harder areas and can't get the gear until we get into the harder areas.  Anyway it is what it is, I at this point can't even clear the very first wave in hard - boy is this area hard.  I get it's end game stuff and I'm not ready.  Thanks for the responses

It's tough for sure, no disagreements there. :) You'll get there.

But the Forge is great and even shots at good one-off pieces of 5-6* (especially 6) is big. 

More or less, yes. The set bonuses from DT gear isn't useless and a source of 6* gear is always nice to have, but given what resources you need to be able to actually farm hard DT it's somewhat lackluster. FW, at least in my experience, allows you access to 6* gear long before DT hard is a realistic farming option. Farming dungeons likewise. Dragon 24 has nothing on DT hard, which both  takes me much longer and in many cases won't allow me to auto it.

The only material I actually farm in DT is the aforementioned magma cores, not because I desperately want fatal gear, but because it's the only boss that I can beat quickly on auto at this point. Even then, the amount of legendary material I get out of it is very limited. Even after several rotations of pretty much farming the magma cores exclusively, I still can't forge more than about 50 pieces of 5-6* fatal (of which most will be sold anyway). For every piece of fatal gear I can use, I'll likely get several pieces from other non-DT sets that are equal or better.