Boot Hill

Just got this achievement, take off your gear (this will help with speed) and just run in and die 30 times. reequip your gear and finish the instance as normal. As you die you will see big metal THINGS pop up right inside the arena, thats your tombstones. 15 will spawn on either side when both sides are filled you are good to go. The zappers are a great way to ensure death if you are struggling actually dying with the followers.

edit to add: you need to finish the instance to get the achievement, also the timer is not a "finish in timer or fail" timer, its for bonus score so the timer is irrelevant.

You don't have to finish within the time limit, i just died 30 times myself by going in naked (in solo instances your team members death doesn't count) and finished after the timer was already gone and I did get credit. You can see the 30 tombstones left and right just when you enter the arena, so its easy to keep track.

This sounds like the complete opposite of a "feat of strength"