I think heavy armor or high IF is important for a shielder. People often say the opposite, stating that the shield is your armor, or you shouldn't get hit a lot of you are shielding well.
I've played sword and board for a couple gens, and I find that I need extra survivability for TEAM HITS! :p I'm serious. As a shielder you are usually up front (or should be) and often face hugging the enemy. Your team will hit your back and sides a lot.
Nothing worse than engaging the enemy with only 1/4 health cuz you got knicked twice by a teamie and were wearing light armor.
Just a thought!