I don't like it because you are not guaranteed to win it even if it was your 10th try. Each attempt is an independent chance that does not effect the proabability of any other attempt. As there are only so many attempts, logic can only take you so far. The amount of goods is less important than the random nature. Additionally let us compare a DC with a complex negotiation to the 48th and final level of GE. Both require 8 goods for each negotiation, but the 48th level gives you a 50 percent chance to get something like a terranced farm, while DC challenges at best give something like 5 percent chance for an indian palace, and GE even gives you an option for battle if your city is developed enough. Sure DC gives you one more chance, but the ratio is still lopsided between the two.
What irritates you about negotiating - that you can't control it entirely due to a random factor- is exactly what I enjoy. It adds a challenging dimension to the task. If you work steadily to improve your negotiation skills, you
are guaranteed to win within only a few tries. I've done so each week for the past 10 months - needing a range of 1-3 tries to successfully win even the most complex negotiations every time for all of GE, quests & events. Others will tell you the same.
As for comparing the prizes for DC vs GE... We get 365 DCs in a year. To win a DC prize, we only have to do 2-4 different basic tasks. We get 52 GEs in a year. To win the top prizes which are on its 4th level (not including TOR relics), we have to work through 48 fights/negotiations of steadily increasing difficulty just to get to that level + another 16 increasingly hard tasks to get to the final prize. Without spending a bunch of medals for extra turns, it takes a few days to fully complete a GE. The fact that both GE & DC have negotiation tasks is irrelevant. GE has far fewer chances to win per year & far more effort/time required. That's why GE's top prizes (diamonds, TF, etc) are typically better and with better odds.
Just because GE gives a choice between fight & negotiate doesn't mean Inno should give that same choice for everything in game. It's intentionally designed to include both passive city building & active fighting, wanting to encourage growth in both aspects for all players. But, many folks who mainly fight will perpetually complain about negotiating. And many folks who mainly negotiate will perpetually complain about fighting. Oh well, such is life in FoE.