As I’ve outlined in detail in other related threads (so this is brief) I have an issue with the fact that dual spec dilutes the role play agency. The game is about picking and crafting a character. There is provision for respeccing - a cheap and easy option. But dual spec fully dilutes that sense of identity and breaks that important role play aspect to the game.
I will bend on PVP, it is separate and RP is a less defining factor. It needs action to increase participation. On that basis I support the idea of an arena specialised spec.