TankPoints ranking is not that great anymore, and I will be removing it from future versions so I wouldn't recommend it.
Slider positions are always a bit personal, and depend a bit on your gear level. The defaults probably could be updated slightly based on newer gear levels, really, but basically it depends on what you're looking for.
Mitigation Scale is often used by people with minimal weight to Mitigation in order to isolate the highest EH (Survival) items.
When gearing or optimizing for survival time rather than EH, I would recommend using Burst Time rather than Mitigation Scale weighting.
Typically the best results IMO will be from Optimizing for Burst Time while also setting a minimum HP criteria. You can also always do it the other way around and Optimize for Effective Health while setting a minimum Total Mitigation % criteria.
There are tons of ways to approach gearing a tank, so pretty much have to select the methods that work best for you.