If you look at things from Blizzards point of view though, theyve created a successful class that is enjoyed by the majority of people that play it (otherwise they wouldnt play it).
You statem Shamans are boring, yet many people also enjoy them. (I happen to think they are good fun too).
Buffing a class because they arent competitive almost alwyas comes hand in hand with their population numbers anyway. (ie people dont play a class they cant compete with, which naturally decreases population numbers therefore justification for a buff).
And dont get us started on rogues
Rogues have dominated in one form or another every single season of PvP. Including season 5. Many many people play rogue. Most rogue opponenets dont enjoy being stunned to death. That means the chances of rogue getting PvP buffed atm is virtually zero