A few tidbits to add to the analysis:

1- Your character can fill the role of tank without being tanky by placing a large number of beefy undead between enemies and the party. A mid level DN can easily put 1,000s of HP onto the battlefield.

2- If you still want to tank yourself, remember that you can use Magic Jar (or if your DM allows dragon content you can learn the 4th level Bloodstones Frightful Joining from 348) to inhabit intelligent undead (Necrosis Carnex, awakened skelletons, etc.). That way, you can give your frontline DN a very beefy body.

3- The party composition has a lot of potential (assuming your DN and the Druid don't kill each other). If you can convince the Blaster to focus on cold and use the Lord of the Uttetcold feat, then the blasting will deal no damage to undead and will actually heal cod resistant/immune undead such as skelletons. This would be doubly effective if the summoner druid takes Rashemi Elemental Summoning to summon Orglash's that have Cone of Cold. In essence, use your skelletons to hold foes while the Blaster and summoner freeze your enemies to death.

4- If you decide to go heavily into minions, make sure you are organized so your turns go by reasonably quickly. This is doubly true since the party already includes a minionomancer.