I have 4pT15 HC and now I also have 4pT16 Flex so there is no much difference of stats (543 vs 548), I think the 5% crit on pyroblast (which is the most important damage source) is better than the bonus of T16, so I'm not sure if I should change the tier.
In general I think the bonuses of this tier are the worst of this expansion so far, really disappointed . As arcane there are no doubts that T15 is much, much better, frost well... is not suitable for pve if you want to maximize your dps and as fire... what do you think?