Actually, you definitely have a chance to survive on divebomb screw ups. In fact, about a week ago I did t5 to get 2 people their wins. 3 people got hit by the divebombs and got pushed into the arena. Then they just stayed there, running about as twintania finished the other 2 divebombs. One person that was pushed the first time died, but was raised immediately after (we won that run iirc). Also, I've had t5 attempts where some people did not stack for fireball in time and died alone (or caused a 2nd person's death) but it was no where near enough to cause a party wipe. Most of the 'one person dies, everybody dies' in the game are caused by a strict dps check that are completely thrown out of the window when you give a party 20% echo.
Also, healing in this game is overpowered in terms of how fast you can heal from near 0 to completely full. I don't know which design led to which, but if instant kill mechanics goes away but healer's healing power stays as it is, alot of fights would suddenly be near guaranteed wins. Twintania's death sentence is not even an issue to think about in parties now. Just heal it after it happens, no need to think about when it's going to happen and when to use mitigation skills (I certainly didn't when I tanked and healed the fight recently). Divebomb phase where there's no instant kill? Players just get hit by the dive bomb, hit the wall and...nothing. Targetted twice? Long enough to be fully healed back to full before the 2nd dive bomb. Twisters phase with no instant kill? Twisters itself wont kill so healers can just heal people in 3 seconds or less. Dreadknights now only saps people's health slowly? DPS can be slow and let the dread knight peck at the stunned party member for a few seconds and he/she won't die and will be healed back to full in seconds. I won't say no removing instant kill mechanics in raids but that's probably going to need a lot of rebalancing to player stats (which alot probably won't be happy about) plus rebalancing past fights, especially level synced ones.