this has been written extensively 2-3 months before the last big patch .. the best gears for all classes for lvl 90-99 are socketed SoO gears with (if you have it) 3 socket heirloom 2H weapon or 2 socket heirloom 1H weapon .. trinkets are a wide mix, but most class'es BIS are still neck, cloak and rings BOEs, if you can get socket or leech on these BOEs even better
my SoO
https://worldofwarcraft.com/en-us/character/us/nagrand/cæléstråsz outperforms my BOE
https://worldofwarcraft.com/en-us/character/us/nagrand/cælësträsz by about 14% raw damage, and range ability attacks are also increased by about 14%
give you another example, plate chest ..
Shaladrassil Chestguard is ilvl160 = 40 str 61 stam 17 hast 37 mast while a
Chestguard of Cyclopean Dread is only ilvl130 = 44 str 64 stam 17 has 16 mast 20 versa (after socket with 3* 5str/6stam gem with 20 versa enchant)
so, do not buy the BOE until you have the full set of SoO, after which you can check if they are worth replacing .. many 99s were saying that epic drops are also good, you can check that again when you have your SoO gears to compare with and swap out if needed
all my 99s were full BOE, which cost me a lot of gold, but i have to slowly change them back to SoO gears, the pain part was they were all SoO geared before legion and i had deleted those and replaced with the BOEs
if you want to play this bracket, start getting these SoO gears right when you are lvl90, they are good, i am raising a new set of 3BDKs and 3MMHunters to move up to this bracket at the moment, i think they will be fun in the 90-99s xp-off bgs