The issue with three of the four tank stats is that they don't work very well. For instance, defense only works against melee/ranged white damage, which wasn't too much of a problem until Bioware decided that EVERY tank mod would now have defense. Shield and absorb are linked together, and both are kinda worthless because you can't shield critical hits, and the average crit chance these past few expansions has gone from 20% ish to 40-45%, making both shield and absorb a lot less useful.
The only tanky stat left of you really want to be a meat shield is just to stack endurance for more hp, since that works against crits and yellow damage.