One of my canadian buddy told me that immigration officers are very particular about the job experience letter. He said that experiences that are copied-and pasted as is are a bit questionable in their standards.
What I would suggest is for you guys to make an appeal by sending out a letter along with a copy of that decision and resubmitting a work experience letter not just from your HR but also from your direct line manager. Don't lose hope, try to make an appeal and who knows, it will make a difference.
Don't lose hope. If you really want a canadian visa, take action!

There are a lot of people in this forum who have applied several times before getting a visa, so carry on and Good luck!