Yeah -- that's the kind of build I was talking about!
Paladin10/DDefender10... that works. Might want to swap out a few Paladin levels for something else, or not.
However, it seems a terrible oversight with a Charisma of 28 to fail to take the leadership feat, scoring yourself (at level 20) a level 18 cohort, such as:
1) Cleric18, or
2) some flavor of fighter/rogue/etc. devoted defender.
I'd probably go the Cleric route, for the always-on buffing potentials and the fact that the only thing scarier than a 400 HP tank is a 400 HP tank who can be "healed" 5 or 6 times a combat!
Also note the pleasent synergies available, i.e. death ward, etc. etc.