Added. I remember a Lesser Ward being life-saver in Bleak Falls Barrow on a low level character
Regarding dual-casting, it depends on the character. Pros - 2.2 times more AR => more spells can be blocked. Cons - 2.7 times more cost (which, in case of wards, becomes huge), inability to attack (perhaps Mzund can work, haven't tried it). I prefer drinking Resto potion, it can make single ward twice as strong and should be more than enough to combat any mage, assuming you use Steadfast Ward (with Shalidor's Insights Lesser Ward can work as well).
Added. I remember a Lesser Ward being life-saver in Bleak Falls Barrow on a low level character
Regarding dual-casting, it depends on the character. Pros - 2.2 times more AR => more spells can be blocked. Cons - 2.7 times more cost (which, in case of wards, becomes huge), inability to attack (perhaps Mzund can work, haven't tried it). I prefer drinking Resto potion, it can make single ward twice as strong and should be more than enough to combat any mage, assuming you use Steadfast Ward (with Shalidor's Insights Lesser Ward can work as well).