Well my toughts of your Lord Marrowgar:
1. What kind of tactic you use? Overal raid dps is really low...
2. You had enough MW to hit LB 45 times, you used LB and CL 35 times. Are you using soundwarning? That helped me alot.
3. Flame Shock was up only 2.5 mins. Fight duration is close to 6.5min. Thats one of the best spells we have in that fight since you need to move.
4. Top 3 abilitys are from auto-attacks. You are leaving a lot of CD:s unused.
My advice:
1. Stay in melee, at all costs. That whirlwind/bonestorm/whatever does minimal dmg.
2. When it leaves you behind, FS. If for some reason you cant get in meleerange (it is huge btw) use shocks and cast LB.
3. You can run over that ice-stuff, just do it quickly. Keeping SR up all the time in this fight is polite
In my guild i'm in top 3 every time we kill this, 8-9k dps. Usually i'm best melee, since we have soooo many ranged abilitys to use.
PS. You have 31 expertise in your mainhand.... drop it to 26. OH expertise is not so important.