At this point, looking back on the new coil turns (at least 6 through 8) my feelings are mixed. T7 feels like the only well designed encounter between 6-8, especially when you look at longevity (this crap has to last us 6 months).
Turn6, even in all i90 we were able to ignore any mechanic past 40% and just burn the boss down. I still don't even know how those mechanics are supposed to work between the slimes and the slugs. This turn will be even more of a complete joke once people are geared up even more. It already is on loot piñata status. The sub 40% mechanics should have been more pronounced for i90 so that ignoring the mechanics and just burning the boss should not have been viable.
Turn7, I like it. Too much dps and you push phases in weird directions or cause chaos by having too many things going on at once. It becomes wise to manage the timing of mechanics (with more and more dps will require constant group tuning of when to push). That combined with a large section of mistakes being autowipes gives this turn fun-longevity in my opinion.
Turn8 currently is the worst designed turn in my opinion. Allagan field and timing towers is a good mechanic, but there are three major problems with this turn that make this turn already easier than t7 for progression groups (and should be in the top10 of a "Do not do" list in raid design).
It is a veritable striking dummy (so if you have the means to do so, going 3 monks and a bard is ideal). Combined with the fact that in essentially i90 gear if you push dps enough you can skip tower phases, god knows what will happen when you are fully geared.
At the top of the list of poor design choices, though, is brainjack. It is trivial to bypass the mechanic by just placing a person near the center of the boss. It should have been designed to obligate a tank swap: It is embarrassing that this turn can be single tanked, let alone have the ability to never need to tank swap if you do bring in 2 tanks.
Ballistic missile is also too easily countered. Stacking trivialized any of the challenge involved and it devolves into a very simple algorithm to solve it. Simply altering the mechanics so that if the yellow markers overlap causes instant death would make ballistic missile a lot more fun by requiring more than 3 people to be accountable for passing the mechanic check.