kernal_task bringing MacBook Pro to a halt - fan problem?
Do you also notice the MacBook getting much hotter on the right side than on the left under load? This would confirm that the right fan is not working, so it wouldn't be just the sensor.

The kernel_task issue is a recently discussed topic and it is often caused by high temperatures. Take a look at this active discussion.

I would replace any broken fans and distribute external hardware that draws power and the power supply evenly between right and left ports.