Everyone is hating on hero party and hoping to see them get whooped for kicking mc out, but imo this is one of the better things they could have done. With mc as their tank they would never have realized they were taking damage and continued to make bad habits. Now they will easily be able to identify the issue and actually grow in their profession. It is also safer as eventually they would have run into an enemy with attacks that insta-gibbed the tank as it hurt the entire party at same time, causing as many times the damage as there are people in the party. And then they would have died themselves. With an evasion tank they will notice they take damage early on in the dungeon, and probably even already keep dodging in mind as they are aware that the evasion tank wont be there to block attacks for them.
Although as ppl say, odds are that for plot the hero will start blaming others for his setbacks. How else is the tanks harem supposed to decide to leave hero party and chase the tank instead? Most likely he ends up putting blame on evasion tank, so that she also joins the other girls in the chase to become tanks harem.