It takes about 2-3 hours to get in an alliance roulette as a tank. My suggestion is to switch the party comp to 2 tanks 4 dps 2 healers per party even if temporarily. This is the only content in the game with such a low number of tanks are allowed in.

This rewards a high amount of exp but you are waiting such a long time to get in. Shouldn't have to wait 3 hours for an alliance raid.