I diagree. First off I think its not bad design because we are talking about the casual content. Its not like all content is designed to be passable without interaction, in fact, most content is designed where if people aren't doing what they need to do, it isn't at all passable. The CT chain was put in the game specifically to be simple enough for everyone to be able to complete. On the flip side, I would say if it was too much more difficult it would be poorly designed. No one wants to beat the odds of needing all 23 other random people to be competent in order to pass. The content would never be beatable if that were the case. Its designed so that it can be completed with just enough people pulling their weight.
The other part I disagree about is your call out on other games trying to kill you all the time. With so many one shot mechanics, how is this game NOT trying to kill you all the time? Its the one shot mechanics that demand people to play and interact. If its not gonna one shot someone, odds are that person is just going to ignore the mechanic. I would even argue other games don't try hard enough to kill you all the time. Too many forgiving mechanics exist in most other games and this is so much more clearly the case for DPs classes in other games. DPs have the derp stigma associated with them specifically because other games hardly ever required the constant survival and awareness. It usually came down to tank and heals holding everyone's hand and managing mechanics on their own. If DPs had mechanics, it was hardly ever more than one or two of the DPs. This game designs their fights where DPs have to be aware of what's going on so they can survive where other games had DPs just stand there and do max DPs.
In fact, just about every point you mention about other games exists in this game too. Constant damage is there, managing resources, including time as a resource. The enrage mechanic is something though that I don't recall being so prevalent in other games, but that's only because DPs requirements weren't ever so tightly limited in most cases. Those fights were usually designed so that you would more likely run out of mana and such before you would run out of time, but enrage mechanics definitely existed.
I don't know though honestly, I can't follow your logic because most of your points about how other games do it applies to final fantasy as well. FF has given more responsibility to DPs to play well than any other game I have seen, and the same basic mechanics exist on both sides with healers and tanks managing constant and burst damage, not standing in fire being less forgiving in FF, and time has more value as a resource than in other games because of tighter enrage mechanics.
What I absolutely do agree with you though is the difficulty curve is off in FF. The game takes a huge jump that most people aren't capable of adjusting too either because of difficulty or the lack of gradual increase.