Assassins are always good to have a few of. They are delay tactics, especially if you can get them in a supply line of ferrying commanders.

Unless I've had assassins fail before because of Banishment, I usually equip at least one of the following.

Lifelong Protection
Eye Shield
Skull Talisman
Dragon Helmet
Medallion of Vengance
Bow of (Anything)
Faithful
Antimagic Amulet
Lead Shield

The only time I make a 'super' assassin is if I get an assassin that gets into the HoF with something decent (Like Quickness) or a Succubus.