The majority of that Chelsea team have won the league before. I think that makes a huge difference. Until our players prove that they can last the distance without caving in their strength in character will continue to be up for debate.
I also think it's a bit disingenuous to use last season to question their strength in character when it was clear certain players had issues with Mourinho and visibly stopped playing for him. Whether this was right or wrong is another debate all together.
I do think Chelsea will come unstuck at some point this season because there are flaws in the system they are playing and teams just haven't been able to fully exploit this yet. City certainly should've beaten them.