More Future Job Changes?

So you want them to replace the current mechanics of Power Guard/Reflection?
Because there's absolutely no way they would give us two skills that deal damage on contact.
Take away the damage reflection from Power Guard/Reflection and all you have is Achilles which would clearly be repetitive and, thus, removed.
I'll keep Power Guard, thanks.

By the way, the only things that makes a tank a tank in gaming are the ability to withstand a great deal of damage and (optimally) ensure that they're taking damage instead of other party members.
So your definition is a little skewed since being able to roll over lower level enemies isn't a prerequisite.

On a final note, it would make absolutely no sense for damage to be dealt based on the attacker's defense for several reasons including the need to create an entirely new formula for one skill despite the fact that Big Bang was designed to simplify the game.

Then just make Power Guard like body pressure? Make it's damage based on the attack range of the user? Then it would have all the benefits of 'high leveled warriors just squishing slimes on contact' while it doesn't require a new formula.