One thing I've been thinking about for a while is that we often fail to accurately define "skill" when it comes to arenas.
I would make the case that there are two kinds of "skill" or "finesse" or what have you in arenas (and to a lesser extent in RBGs): Dynamic skill and Static Skill.
Dynamic skill: this is how well you perform in a scenario that features two roughly balanced but entirely different opponents. This is most similar to a card game (like Magic: The Gathering or Hearthstone), where there are 2 opposing decks and the assumption made is that they will be entirely different but balanced (assuming that both players are competitive and in a non-mirror deck matchup). The better player is the one that recognizes their opponents strengths and weaknesses and focuses on negating/exploiting them.
Static skill: this is how well you perform in scenarios that are almost purely mirrored. This is most similar to a board game like Chess. Both sides have access to nearly the exact same resources (but not necessarily; I.E., in chess one player has to go first) and the winner is the player who mini/maxes the best. As a whole, we generally consider games that require static skill to be relatively boring (Thus the decline in chess play in recent years), although they are almost inherently more likely to be balanced than games requiring Dynamic skill.
The general dislike of 2v2s in WoW arenas is because games are either Rock-Paper-Scissors (no one is happy,) or similar enough that they require Static Skill to win. While I agree that Rock-Paper-Scissors games should be avoided when possible, I disagree entirely with the sentiment that Static Skill in 2v2s is somehow not rewarding or difficult. In fact, in 2v2 matchups the better team is almost certain to win if the matchup is Static (and of course not Rock-Paper-Scissors).
There can be a bit of dynamic play in 2v2, since some matchups are similar without being mirrors (
Disc/Ret vs Disc/WW comes to mind). However, even in mirror matchups the team that utilizes their abilities at the correct times and in the best combinations are going to experience a rewarding win in my opinion.
EDIT: One more thought: In Static 2v2s as well as in Chess, players generally appreciate the subtle gameplay far more once they themselves are experienced in those games. The barrier of interest is high in both of those cases, which is probably why those game modes are seeing a decline in popularity despite being balanced.