I think the armour issue goes back to Vegetius mentioning that troops petitioned not to have to wear armour or helmets - http://www.sonshi.com/vegetius.html
The exact section eludes me at the moment. I know that there is debate about whether Vegetius was in fact indirectly alluding to Gratian's Alan foederates whom he showed favour to and which caused him to be overthrown and/or guard units on ceremonial duties, or whether indeed actual front-line troops were included in his comment. I think it is worthwhile remembering that the state fabricae are shown in the Notitia explicitly manufacturing several types or armour - and also that I cannot personally recall reading any military history of the ancient world where troops petitioned to remove armour and helmets?! Can anyone correct me in this?