No sooner than 2pc T15? Or would you be alright with replace one slot if you were upgrading from a 484 to 522. Not sure what the value is on the 5% PoF
Well, the 4 piece gives 5% extra strength for 20 secs every 60 seconds which comes down to ~1.66% extra strength. (5% strength with 33% uptime)
I'm not sure of your gear so you should compare the current piece + 1.66% of your strength with the piece on. ( Probably somewhere around ~150) Then apply the stat weights for both and see which is higher.