Les Parisiens bounced back from their 2-1 loss to Benfica in the Champions League thanks to goals from Thiago Motta, Zlatan Ibrahimovic and Edinson Cavani.
And it was the Ligue 1 champions' reaction and performance in Lorient that prompted Blanc to express his satisfaction, after demanding renewed effort following Tuesday's European disappointment.
"This is an important victory and deserved I think," the 48-year-old told reporters.
"We got games against Evian and Benfica wrong because we did not put enough effort into two difficult matches. Tonight, I am happy with the win, but also with the manner we won.
"We scored three goals away. The boys played very well with and without the ball. When we lost possession, everyone fought to get it back.
"If we want to be a great team we must have the right mentality. When you achieve the right ingredients like tonight, we are hard to beat."
The win ensures the Ligue 1 leaders remain two points clear of title rivals Monaco, who beat Guingamp 2-0.