That is, keep adding 5 seconds to the respawn for each death a player has. There really needs to be a bigger punishment for dying THAT much, regardless if you are a tank or not.

25 seconds is long enough I agree, but I don't see why you should cap it at that. Players who are bad should stay out of the field more to prevent feeding (intentional or not) and learn a lesson in playing it safe and strategic, learn when to retreat and when to fight, and not just herp derp go inside a pack of enemies plz ima tank/dps.