I love the show, but hate how they portray the Anglo-Saxon armies.

We have very few written sources that describe details of fighting from the late 8th / early beginning of the 9th centuries. All the available art portrays armies of massed men, however, and it's almost certain that the Anglo-Saxons were fighting in shield walls.

The show doesn't portray them this way, I suspect, in order to show the relative inexperience of seemingly civilized but inept English armies compared to the barbarian ferocity of the war-hardened vikings. It's problematic on several levels: the English fought a lot of wars against each other, their armies were composed of lots of non-professional levies (so, less uniforms and more individuality, like the viking armies), and why are the English wearing bad copies of the (also inaccurate) armor made for Braveheart, which is set 500 years later? I suspect they didn't think (and this is stupid of them) that their audience would be clever enough to spot the more subtle types of tactics that allowed the vikings to win in shield wall vs shield wall fights.

The battle between ragnar's landing party and the northumbrians who cut them off from their ship in season one is probably the best in the whole series for portraying a rugy-like kind of shieldwall fighting that was probably much closer to the norm.