So I've been missing out on 10k XP because neither of these challenges work. Anyone else having the same problem?

They are both currently bugged at the moment. The problem is that they are not retroactive and so if you gain a single level in Armor or Stealth before unlocking them they become impossible to complete.

You start at level 1 and need to gain 11 levels to complete the challenge. If you unlock Invisible War and already have level 5 Stealth then the highest you can get this challenge to is 7/11.