To be quite fair to Quebec, there is a general distrust of the "federalist" approach -- whatever that means -- at the moment, so they'll vote in a separatist/provincially minded movement simply if it suits their ends.
The NDP has to try hard to win back the support of Quebecers. Mulcair can do that, but he needs to really work at it.
Mulcair and his potential as the successor to Layton has been discussed to death by the media here. I'm not sure he'll be as popular as Layton. The popularity of the NDP here in QC is pretty much the results of Layton himself. Mulcair still has the image of the provincial minister that was demoted or in better terms asked to leave the provincial liberal government because of all the troubles he stirred. I mean, he was attacking the prime minister in public while he was himself minister or the environment. There are also a lot of rumours about how it's apparently hard to work with him as he's selfish and prefer his own ideas to that of others.
I would trust more Brian Topps than Mulcair to be honest. In any case, both don't have the charisma of Jack.
People here also have the habit of flip-flopping often when voting. We almost lead the ADQ to power only to completely eradicate the party in the following election.
If the NDP want to keep their seats here, they'll have to convince people that the candidates they presented and that won were not simply placeholders candidates because no one else wanted to run for the NDP. Unfortunately, many of these newly elected MP were in fact placeholders. Some were undergrad students with no political experience, other were low wage workers with no education and some were retired people.
It doesn't help that Lise St-Denis, the NDP MP which was elected in Jean Chrétien's riding decided to leave the NDP for the Liberals after talking with him. She even said that the Liberals' program was superior in her eyes to that of the NDP. Add to the fact that some can't speak french or don't even live in their ridings and you get a complete disaster and a party that seems to be run by a bunch of amateurs.
Hilariously, Ruth Ellen Brosseau might be one of the few that is guaranteed to be safe unless the other parties offer more prestigious candidates. You know the one that was in Vegas on a trip on election day. While she was definitely one of the worse MP to be elected, at least she quickly (or Mulcair did) worked to damage control everything. She moved in the riding, took intensive french lessons and appeared at all major local events. The whole "scandal" also brought her some notoriety. She's the equivalent of a reality show candidate.