Oddly, some of the most interesting theorycraft/math that I've read comes from a non-tank main who only has one tank at 60. Most people hardly notice if it's done well.

There are situations where theorycrafting on a job that you don't actually raid on will lead to some fairly obvious blunders (especially on a job like DRK), but it's still helpful to read these. Intuitively knowing that something is sub-optimal isn't the same as knowing why it is sub-optimal, and scrutinising these errors in reasoning forces you to think about your job and your playstyle in more depth. You should be verifying everything you see in here for yourself anyways prior to making it part of your rotation.