Djokovic was rolling in the wet stuff before the rain delay. When he came back his momentum was gone and it was back to even basically. And Federer in '11 played better in the start when it was sunny IIRC. Haven't seen the highlights of that one in ages.
Important thing to point out though, is that with 'wet conditions' we don't mean the disgusting conditions of the third set of the RG 2012 final. Those were conditions where they should've stopped and is not something we need to associate with 'playing' conditions.
Wet conditions should be simply more damp, but still playable. And in those, Nadal still has no problem with anyone despite it favouring other players.