Short question, I have 2pce feral tier(561) and 1 hc warforged chest and 1 hc legs. I have tier tokens for 561(normal) version of those slots. Would the tier 4piece be better than the extra stats from the hc warforged and hc going down to normal?
According to simulation, it's not that good. The average gain is that you get more FBs. However, it's possible that the action list doesn't intelligently use the proc.
In practice, people seem to remember the times the proc provided a clutch finisher or that extra PS+HT when needed. The fact that we all make mistakes and can't predict the future give this bonus value however I still question it's unanimous use. Since a lot of people have content on farm, I'd encourage you to try running 2p with two s instead.
In essence, ignoring the procs that occur during the fight, the extra PS+HT on the opener and the extra PS+HT when you enter BitW phase make this bonus a poor man's Nature's Swiftness. Even a single timely NS use during a fight is a lot of value. I forget the old numbers but it was at least a few percent.