It could very well be partly the healers(s) fault. Duty Finder healers pre-30 or so seem to over heal like there's no tomorrow.

A couple of pieces of advice:

1) Start every fight with tomahawk and then overpower as they run to you. Starts with very nice head start especially on tomahawked mob.
2) Mark your targets (1, 2, 3) (keeps dps focused)
3) Make sure you are using flash from gladiator. As a Marauder you should maybe use it every 3rd or 4th rotation. Use and abuse Heavy Swing > Skull Sunder combo.
4) Throw in an overpower once in a while as long as you keep the mobs in front of you.
5) If one does run away your best bet is to tomahawk it. Running after it isn't that effective because you are wasting time running while the healer is gaining more aggro. Tomahawk and overpower when it gets back in formation.