There has never been nor will there ever be a season where EVERY class is EQUALLY glad viable. Right now ANY class can get glad, and basically every spec. Less specs can get rank 1 right now, but given its like the top 200, any class except MAYBE deathknights can get rank 1 right now.
These are the statistics for gladiator in season 8
Priest: 291 - 15.08%
Paladin: 288 - 14.92%
Shaman: 279 - 14.46%
Warlock: 233 - 12.07%
Warrior: 189 - 9.79%
Mage: 161 - 8.34%
Druid: 148 - 7.67%
Hunter: 143 - 7.41%
Death Knight: 104 - 5.39%
Rogue: 94 - 4.87%
These are the current 2200 statistics, which is basically gladiator.
This obviously doesn't account for population differences, but I don't see that much difference in terms of parity. Some classes at the top, some classes in the middle, some classes at the bottom.
not sure why rogue is 3rd worst when rmd is like god comp of s12/13 must because most of them are s11 rogues might exsplain why rogues are bad