Rokmar the Crackler Abilities & Tips

Rokmar the Crackler is the second boss of The Slave Pens in Coilfang Reservoir, likely a giant racial offshoot of the Makrura.

Grievous Wound: A bleed debuff, it causes Rokmar's current target to bleed for 900 physical damage every 2 seconds until the player with the debuff has been healed to full health; and Stoneform will also remove it. The debuff is not timed, and will last until you are dead or cured.
Water Spit: AoE, deals 1600-1800 frost damage to nearby targets. Frost resist gear would be useful, as it would save the healer's mana and the healer will not aggro that easily. But it's not necessary if you have strong dps. The range is 40 yards, so Hunters/Mages can stay out of range, depending on spec.
Ensnaring Moss: Decreases attack speed and casting time by 50%. The spell is ranged, about 30 yards. If you are healing, be sure to get out of this. It's a sure wipe if you get it since you have to keep your main tank topped off.
Frenzy: Heroic Mode only. At 20% health he enrages increasing his physical damage done and attack speed.

His water attack is frost based, so frost resistance of any kind is good.
To prevent a wipe if the fight is not going well, you can jump into the water and you will exit combat mode after a moment. Make sure that you get out of range of his water spit.
His most devestating attack is the bleed effect, which will increase the already tremendous amount of damage per second over time. The only way to remove this is to heal the afflicted member to their maximum hit points. When this is done, the bleed is removed.