"Aggro Battles"

[Warskull]

Aggro = damage dealt or healing done. Tank stance just puts a multiplier on it. So the highest DPS tank will generate more aggro. If you have better gear you may pull aggro. Gunbreaker and Paladin do better DPS than Warrior and Dark Knight, but in practice I only really see a Gunbreaker pulling agro from a Dark Knight. On a longer fight a gunbreaker might pull from a warrior.

The off tank should have their tank stance on. They want that extra aggro so that on the off chance you die, the boss goes after them and not the healers. If there is a significant DPS gap the off tank can shirk you on occasion. However, if they are pulling agro with raw DPS they probably outgear you and would be the better main tank. There is no way for you to fix this as the main tank if your off tank out DPSes you.

What you are describing sounds more like them using provoke to intentionally pull agro. After dying the should be behind on agro and unable to pull from you again without a provoke. If they insist on being the main tank, let them. Some people have to learn by touching the hot stove.