You need several shields like the above posters said.
I would favor fire (AoE) and a blind shield, If you don't wanna spent time and money on a full set (+10 AL vs. various types of damage + 20% Blind & Cripple reduction = 7/8 shields).
I recommend though to get a full set for at least the command line. Don't bother with any inscr. that's gives physical damage reduction, they are by far inferior to any other mod.
You also might consider to get your hands on blue req 7 / 15 AL shields for command. Come in handy if you don't wanna spec high in secondary attribute lines that you aren't using much, due to godly pve-only skills.
For DoA (and late Nightfall) you want one of the shields with + 10 AL vs. Demons aka The Stygian Defender or The Stygian Aegis. They are not that pricey anymore.
There is a collector in Eye of the North for a req 9 insc. Motivation Shield (Aureate Aegis) with an inherent + 30 HP mod. You only need 5 stone summit emblems for them, which are easily farmed doing Killroys repeatable solo dungeon. The collector (
Marduc Snakeslayer) is just around the corner.
Hope that helps.
Good luck and have fun.