Arenas ruined PvP. It's an unpopular opinion and I can almost feel the rage boiling, but let me explain:
When you think about RPG battles, what do you imagine? Most likely something like WSG, AB or AV -- A battleground. With objectives. Not just a deathmatch in a small room full of pillars. Now, deathmatch has it's time and it's place, and I'm not here to say it should completely disappear. However, I do think ranked WoW PvP -- and arenas -- needs to evolve with the times.
The problems that come from PvP being reduced to a glorified deathmatch are numerous -- the neverending 'melee vs ranged' debate that in my opinion shouldn't even be a debate. Melee is meant to win in a straight up 1v1 -always- against a ranged due to ranged role in any rpg being a backline high-burst damage character; 2nd problem is this endless arms race of cc / mobility / damage. Hp bloating. Various (failed) resilience experiments to offset the former. Etc., etc. -- All that stems from inherently broken 'deathmatch' arena system that shouldn't have been a benchmark for balance in a game like WoW in the first place.
How can we fix it? Well; For example, they could ape GW2 and bring back a 5v5 bracket with smaller maps that have 3 control points. It'll be a smaller scale tactical engagement with mandatory rotations and generally more objective focused gameplay. Or hell it could even be a 3v3 with 2 points, where you respawn if you die but the time to control points is much shorter than in BGs (think need 200 points to win instead of 1500).
It'd make for a much more pleasant niche than RBGs (when I quit a few months back I didn't have 2 people to PvP with, let alone 9...), and it'll be much more e-sports friendly than -- and let's be honest here -- dead on arrival concept of arenas as they are now.