throughout the entire beta marauder/sent have been known to be by far the weakest of all classes while also being the hardest to play.
bioware buffed them by giving them party buffs so people would actually invite them to groups, since they did low damage, were melee and squishy. they're basically a bard. this helps in pve, but in pvp the zen crap is almost worthless.
they did one thing good in giving them rebuke, which gives them 20% resistance for up to 30 seconds.
guardian/jugg are next on the buff list. hopefully they do a better job.