Individually, yes there is "imbalance". Non-tank builds die in seconds, non-DPS builds rarely lead the scoreboard, etc. But see, most are missing an important point of PvP: Team play. There's a reason we have to choose "Blue" and "Red" at the start of a round.

Leave the killing sprees to DPS builds. It's what they're spec'ed for.
Tanks should not focus on one enemy and stun-lock as many as possible.
Mages should forget about killing, AOE spells rarely land a good hit on bears' and archers' dodge. But, IMO they're the most important class because while helpless alone, they can keep a team SOLID when they know how to constantly buff/heal teammates and debuff enemies.

Take away the notion that more kills = better player, and suddenly nothing seems imbalanced