When it comes to WoW arena most of the comments are unfair. Yes, the composition was a huge factor but having played a retribution paladin at really high rating I felt it was truly high-end pvp with skill being a huge factor. You did meet counters but communication with partners, using line of sight, timing your cds - everything was important.
When it comes to swtor - warzones are a nuke fest, everyone has nearly the same abilities (snare/interrupt/stun/cc/knock back) which is both good (balance) but also a little boring. However, introducing arena would probably create a ton of issues for example some specs being unviable, unbalanced etc. Warzones will get boring eventually though. Arena in swtor - very problematic, world pvp... that's extremely tricky to pull off...
Perhaps space pvp is an option for the future as to avoid warzone boredom?