I wouldn't go as far as to say the 5Dii is weather sealed. It certainly has a degree of weather sealing but nothing to the extent of real weather sealing when compared to the 1D series.
For example, comparing my 5Dii to the 1Diii and 1DsmkII, the "sealing" on the 5Dii is really just "weather proofing." I wouldn't trust my 5Dii in the wet mainly due to it's cheap build quality and lack of 1D sealing.