The loot was pretty good for t5 POI's (most of the time; sometimes I just walked out with brown or orange quality gear, even with a high gamestage and 5/5 Lucky Looter; you win some, you lose some), and the trader rewards were generally worth it, on most occasions. Just my opinion, but there should be an extra incentive for players to scale up the t5 dungeons, something even greater than the possible guaranteed 2000+ dukes at the trader, possibly a great/good//alright item at the trader. A higher chance of getting Legendary weapons (**in A19) or other rare/unique loot (100+ forged steel, a solar cell/solar bank, etc.) at these "ultimate dungeons" would certainly encourage players to loot them other than for the "fun factor". While I can agree - and I'm very confident everyone can - that the T5 dungeons are designed fantastically, I just feel that as well as being foreboding, they should be tempting as well, and the latter is lacking just a little. But hey, I'm not a developer, what do I know?
I've done multiple runs and I've determined that, on average, clearing a few POI's in the same time it would take to clear one t5 dungeon does net you a bit more loot, more dukes at the trader (if they're quests), and with a lesser chance of dying while using less ammo. Basically, efficiency wise, going for the lower tier POI's
can be faster and even a little more rewarding than the t5 dungeons, and I personally believe that should be put into consideration for future tweaking.

Again, this is just my opinion, and I don't consider any opinion to be factually correct. Take from this whatever you please.
While you shouldn't always get a massive win, or close to, from looting, just to repeat what I've said before, the incentive, loot wise, is a little lacking for players to scale these largest dungeons, compared to what they
could be, in my opinion.
EDIT: Just one other, small point I wanted to add to this already lengthy post... If Legendary Weapons are added in A19, I just personally think it would be logical that, since these t5 dungeons are the greatest challenge (to loot) in 7d2D, they should have a higher chance of dropping Legendary Weapons. (Again, those suggested specialized loot chests I mentioned. ^^) You know, with great risk comes the [increased] chance of great reward? (Even by a few %) At least, that's just my take on it.