Honestly, I see teams with better chances of winning the trophy than West Ham or Barcelona.
I believe that a Leverkusen, Lyon, Dortmund, Leipzig or Porto, have more chances of reaching the final.
Apart from Leipzig from your list I don't see any other contenders, the others are too weak for the final and unlikely to make it, well among the whole list then you can also single out Borussia and that's it. Let's see who makes it to the final, if someone from your list makes it to the final it will be cool, surprises in the league are always niceI believe that a Leverkusen, Lyon, Dortmund, Leipzig or Porto, have more chances of reaching the final.
If you reason, Borussia have a chance of getting to the final. barcelona? Well they are more likely to fight for the europa league so as not to embarrass themselves even more, for when was the last time barcelona were in the europa league, they were also knocked out of it? Napoli... I don't know, it will be decided in 1/16, either Barça or Napoli. So it's like this... Basically, I agree with you.
The most critical thing for Barcelona at this point is to improve their performance. They need to get better every single week until their matchup against Napoli. Or they are likely to say goodbye to this tournament.
Saying it is not difficult sounds a bit naive. All those teams qualified in the end and showed they can compete with some of the stronger teams as well. I like to take Sheriff as an example and what they did in the Champions League. They beat Donezk and they beat Madrid in an away game. That goes to show that in just one head to head match up a lot is possible. 
