This was my go to weapon for a long time. However, in addtion to using it with the common flask for auto-restore, I believe that you need to use both the epic/legendary legs for the 75% proc on bonus action (I preferred legendary for the AC+), and the legendary taunt (even if low level) to get the taunt+counterattack up as quickly as possible.
What all of that adds to is the ability to get him into the middle row as a solo taunter and AC buffer for the party in the first turn. It’s the action economy here which is important - I personally found it more valuable to achieve those things on first turn, rather than using the epic taunt + separate counterattack (too much would happen by the time his counterattack came into effect).
Provided the rest of your party has got some good heals and damage going, he can sit there awhile and take it. True, there are insta kills aplenty - but if any of them are resisted, or failed to kill, that player is going to take some damage and find it harder to kill him the next time.