The general rule when using the actual official rules and no house rules is that armour is good when you have ALOT of it. Shields are still good on the offhand for the occasional flukey 6+ save, and are always a good choice with a spear where youc an't use a second weapon.
House rules include a shield and a single handed weapon used together give an additional 1 armour svae for a total of +2 armour save.
Furthermore, there was on the SG Forums (currently still down) a group of trial armour options that the Rules Review Committee were looking at that people were able to play test. The above suggested House Rule was one such option, the others included additional effects with other armour types and I can't remember them off the top of my head.
Hope that helps,