Infraction: Hasn't read a fucking thing
Message to User:
I already hate you.
The rule of thumb I've seen floating around is to keep t7.5 until you have three pieces of t8.5.
For more precision, check the spreadsheet.
Oh, why's that?
It might be helpful to list my armory to make a better decision on this, so here it is... Hope this helps.
The World of Warcraft Armory