as a vanguard Gemaga is pretty easy once you learn where to use your traps. I had a lot of trouble initially. But once i started maining twin sabers with blade destruction and placing my traps efficiently i can tear through there pretty easily in about 4-5 minutes. Not record breakingly fast, but it beats doing chapter 1-1 in story on hard and having to skip cutscenes and skip tutorials and all that stuff over and over again.
give Gemaga a try once you've gotten some levels in vanguard --- You called down the thunder, now reap the whirlwind.