When I play a tank I play a Sorcadin (Hexsorcadin most of the time).

I walk straight into the enemies smiting and if I can with spirit guardians/Bless and far step.

I chase the enemy casters and make sure it will be hard for them to cast.

Most of the time I get 8-12 enemies on me(trying to save the leader/caster).

As a paladin it is hard to fail saves and I have a lot of HP(upcast Aid).
Most of my characters look for a clock of displacement and +x shield/armor/weapon (I like warhammers).

Nobody ignore the block of metal if he is at range and killing you friends while cursing your god.