Again, we have way more interesting matches now than before, and yesterday is the best day in group stages in a looong time. The last matchday will be crazy and almost every team will be playing for something (unlike the old format where teams like us or Bayern played with the B team for the last two matches).
8 spots are very few. Villa has a favorable draw and 6 points already. Us,Inter and Arsenal are the best teams in Europe and we all will qualify. Liverpool is up there, and they have 6 points. That means there is only 3 spots for: Milan, Juve, Benfica, Leipzig, Bayern, Bayer Leverkusen, Madrid, Barcelona, Atletico, Borussia, PSG, Benfica... big teams will have to play 2 extra matches which is huge. For example, next matchday Barcelona plays against Bayern. Whoever loses that match is pretty much out of the first 8 spots. Madrid next 3 matchdays are Dortmund, Liverpool and Milan and they HAVE to win at least 2 of those if not, they are out of the first 8.
And no, teams will not rotate. If you are 1st in the league phase, your Round of 16 will be against teams that were 14-17 in the league phase. Your QF will be against teams that were 7-10 in the league phase. That is a HUGE advantage to get to SF.