I always thought Marauders were horrible to Raid with. I rolled one and took it to 50 on purely PvP, as the mechanics were awesome to play with when it came to that. But raids? I wouldn't dare take one into a raid.
Still hilarious to PvP with though. They were extremely OP for a while, but only for those who knew how to use them and their insane amount of abilities.
If you wouldn't take one into a raid then you obviously don't know the class well. The 15% damage and healing buff provided by bloodthirst is a big reason to bring one into a raid by itself. Predation? Reduced damage to members of the raid and increased speed. It makes the under 60% phase of HM / NiM Kephess much easier when he casts "Gift of the Master's." Kephess pulls you in and even at level 55 many people die before clearing the AoE circle. Predation solves that problem. That's just one example. Marauders have versatile DPS. Rage spec for AoE damage. Unmatched for trashmob killing in a melee class. Annihilation for damage over time via bleeds. Carnage for some of the best burst DPS in the game. Very nice when you need adds downed quickly. The adds in the Terror from Beyond on the Terror itself are a great example of this. I can also DPS cores in HM Operator IX alone. I do not need help on a Carnage Marauder that's not even BiS Underworld geared. Most classes need help with this and almost all of them need help killing adds in the first phase of the HM Terror fight. I don't.
Marauders also get some of the best defensive cool downs in the game. Saber ward reduces damage taken by quite a bit for Force and Tech damage. (This accounts for more damage than you'd imagine), Force camo for some of the best threat drop in the game and reduced damage taken as well as movement impairment effects being removed. Cloak of pain reduces damage taken to you and deals damage back to the other target. And lastly "Undying Rage" grants you virtual damage immunity for a short time.
They bring a lot to the table and some of the best progression teams in the game all have Marauders in their ranks and for good reason. The Marauder isn't necessarily tough to play but takes some work to play well. If you get a good one then they are a great addition to any raid.