Over the years, the Cataclysm community has stabilized in a roughly (60/40) balance between horde and alliance. The PvP activity however, has settled with the exact opposite balance, where the smaller alliance faction actually has a much higher PvP presence than the larger horde. This natural imbalance has accelerated the death of multiple Cataclysm realms in the past. The concept of having a mixed or cross faction battleground has floated around for years, since queue differences were noticed on the earliest cata servers. It would take the death of several realms and servers before this concept was pursued.
Our aim with implementing a Cross-Faction queue is to streamline and balance the PvP experience. There are several important benefits that we have chosen to prioritize.
The primary benefit of Cross-Faction battlegrounds is always the queue time. No player will wait any longer than any other to join a PvP match.
Large premade groups with a high win rate have a chance to benefit teammates they had previously crushed in the game before. We expect this to reduce the tendency for players to avoid each other in battlegrounds.
Multiple large premade groups from the same faction may face off against each other in battlegrounds rather than facing off against a group of solo unprepared players, largely considered boring for both the winners and losers.
When we implement a custom system like this, we need to calculate and mitigate the cons that come with this decision. The primary con of this decision is the possible confusion that comes with having teammates from opposing factions. There are a small handful of factors that cause confusion when teams from opposing factions are simply mixed together.
Player Race - seeing a player of the same race model as your own can lead to confusion. Our solution to this issue is to morph characters into a similar and acceptable model from the other faction.
Player Mounts - seeing a mount identical to yours, or one waving your team's flag could easily cause confusion as well. Our solution to this issue, again is to change mounts into a similar and acceptable mount from the other faction.
Trinket Effects - Trinkets display a very clear icon indicating your faction, another source of confusion. Our solution to this issue, once again, was to change what display occurs when you are playing as the other faction.
Racial Abilities - With all of this morphing to minimize confusion in other areas, we do inadvertently mask the true race of a player. The only solution to this negative effect is mitigation. We have done our best to minimize the number of new race/racial combinations that are possible. We have also put a lot of effort and time into establishing the most similarity between your true character race and your designated Cross-Faction race.
"Why THESE pairs?":
The primary goal of morph selection was choosing the most similar model kit, limited to race options that could also use your class and avoiding as many "duplicates" as possible.
The most extreme scenario of a duplicate in this chart is the dwarf shaman. The horde has four races capable of playing shamans and the alliance only has two. Judging by model similarity, we decided it was best to morph orcs, trolls, and goblins playing shaman into a dwarf for their time on the alliance. This brings us to the situation we have tried our hardest to minimize: uncertainty. An unfamiliar dwarf shaman could activate one of four racial abilities: Dwarf, Orc, Troll, Goblin. In the majority of cases, an unknown opponent could only activate one of two possible racials in a fight.
Undead/Human:Both models are in essence humans of the same scale and relatively similar animations.
Dwarf/Orc: This decision was made based off of their relatively square model (from the back) and heavy footstep animations.
Tauren/Draenei: Both races have heavy footsteps that emphasize their hooves, so this was not a hard decision.
Night Elf/Blood Elf: Their similar postures, voices, sleek models, and spinning jump animations were the primary factors for this pairing.
Gnome/Goblin: Both of these are noticeably smaller than the others.
Worgen/Troll: Both models have slender bodies that curve and lean forward. Their jump and run animations emphasize arm length.