Good tank shield (in General)

Does anyone have any advice to give on choosing a good shield for a tank minion?

depends on your tank..does he cast spells or have a tat?

the kite shield is not a bad choice....smaller penalties on dx and magic...there are many others here who know much more than I...

For my TOA tank, I use a kite shield for the reasons above.

For my minitank, I use a MS. However a MgS might be better depending on whom you fight.

I use a MGS and I've seen the kind of damage reduction it can provide. My favorite is when the enemy's fireball hits his own minions for more damage than it hits my tank. I've used a MS and I can't imagine any reason why I'd switch away from the MGS. The massive reduction to magic is so much more valuable than the marginal reduction to physical damage any other shield.

Sure, it won't help you defeat that ToA tank, but I don't think adding a MS will help you that much anyway.