of course he "shouldn't" lose to players ranked outside the top 8. That's why he is #2, you are not suppose to lose against those players and he never did in Slams, that's why he has been so consistent in his results over the years.
he will do his best, and whether number 2 or not, he can lose making his best, nobody is invulnerable. Fed used to be near to invulnerable in 2005-2006 but it was a long long time ago, it's not the same anymore.
What he "should" do is only doing his best : if he loses, let it be, Fed is no God. He's a 31-year old guy who's had no warm-up tournament and who's used to struggling against the likes of Thomas Schoorel in his first matches of the year. Davydenko was very near from leading him 2 sets to love or 2 sets to 1 twice in this tournament in the past, even toying with Fed for one set and a half in their last match in the Australian open.
PS : I admit that I had made a mistake on your message about Raonic and Tsonga
. Had only seen "Raonic is a tough draw". But I disagree on something : for Djokovic, Tsonga would have been a tougher draw than Berdych, for Fed it's the opposite, yes, but it's a matter of match-ups Tsonga even nearly defeated Djokovic in Roland-Garros.