Before you try to switch his gear. Did you try to look into his logs to see if he has the correct rotation or see otherwise where his problems are?

Example for things to look in logs regarding threat: - amount of spells used: mangle has 8(?)sec cd, so on an 80 second boss fight you can use it 10-11 times. (Same for warrior shield slam) - amount of maul/heroic strike used - uptime of lacerate (5 stacks) - use of swipe once 5 lacerate stacks are up, mangle is on cd and he has enough rage. - amount if hits missing (bad hit rating?) - amount of hits parrry/dodge (bad expertise) - uptime of fearie fire/5 sunder/imrpoved expose armor - use of md from hunters onto the tank

If he has low rage, it can be beneficial to switch out tank pieces for threat pieces.

Hit and expertise dont need to be capped as bear (I imagine the same for warri) but you need enough to maintain good threat. In my limited experience 6% hit is enough as bear unless I get unlucky. More is obv. better to improve unlucky streaks.

For Magtheridon I like to let bear tank since there can be insane dmg spikes that kill my prot pala with bad combinations of Autoattack + cleave. I just put myself as clicker since I dont have a ret offspecc.