You're only going off info that others tell you and haven't actually tried making this into a viable tank set up. Nor looked into why tank viability exists. Can you explain why it wouldn't work in clear terms?
I'm doing a cursory glance at sword and shield mods and I can see some good potential with the right augments on your gear and the right gear choices. You should be able to tank most content aside from something like boss gauntlet which needs precise builds anyway.
What is odd is having such an opinion of finality when you haven't experienced everything in the game, I personally use an "off meta" skill set to tank and have major success without using cow/staff/shield.