Use 3 healers let them kite with a tank or a range (hunter and WLs). kill 5 legs with all your dps then let 2 people kill legs rest on boss fulltime let tanks have one leg in front. You only have 16 legs throughout the whole fight killing them faster isnt a dmg increase might actually be a dmg loss since ranges have to run to them. 2 melees should have no problem killing the leg within 40sec till next leg spawns, we use the front right leg for tanks (looking at the boss) and only tanks. Use bloodlust after the first 5 legs are down an a healer is kitting.
Shadowpriests should dot the leg when its below 20% and WLs if skilled affliction let him dot the leg with corruption to get soulshards. Then you should be fine just keep in mind running to a leg killing it and running back as a caster will make u lose dmg cause there will always be only 16 legs killing them faster is no dmg increase on the boss, if 2 people can handle them perfect if u need 3 try multidotting with one caster but doenst run near the leg.