Originally I thought it was because alliance could not solo compete with premades on honor/hour, so forcing premades to only partial was a good change.
That said, they just moved the premades to AB, and it’s pretty much the same problem.
Horde won 99% of the time because alliance got more rep/hour clicking druids in a circle preventing them from leaving to summon ivus. They got so used to farming horde and turning in crystals, they forgot where IBGY was. Worse, if they got to IBGY, it was only 4-5 players, it’s not enough to hold the choke.
More recently, with the changes(druids now leave after 200 turn ins whether alliance likes it or not), it is definitely above 1%.