Is part of the problem that enemies die too quickly? If so you could boost your style gauge using taunts whenever you can. That might help a bit but can't say if it would be enough. It's probably worth learning which attacks give lots of style too (though unfortunately anything that does a lot of damage or hits lots of enemies will end battles quickly). Red Queen Combo C has a lot of range without being super-damaging IIRC, so you could lure enemies close together and whack them with it.
If you'll pardon the question, are you playing on Human because you are new or just to max your results screens? If it's the latter perhaps some of the others here can suggest some more difficult techniques for raising style.
DF: So why can a Marauder roll but a multiplayer Turian can't? Delta1-9: You are fighting female turian husks. You have reach but they have flexibility.