I usually DPS the legs at the start, if one spawns close to me, and when I have Combustin up. Another thing I do that no-one has mentioned is after spreading my combust to the boss from the leg, I then spread it back from the boss to other legs when IB comes off CD. When we pull, I got straight to then 2nd leg we usually DPS, get a good ignite, pop combust and immediately spread to the boss, I then move over to the 3rd leg and start DPSing it until IB is off CD, at this point I target the body and use IB, this spreads Combustion back onto any legs that are still alive, I've gotten upwards of 4million combustions doing this.
I also try to do it later on in the fight every time I have a combust on the boss and a leg is up.
But if the leg dies to cleaving any way, you would still have lost the potential cleave damage by single targeting it down. You only need 2 legs constantly dead for him to move slow enough to deal with kiting, actually having to many legs down can slow him down to a point were the ranged kiting the boss is out of range for the entire time of kiting witch also is a dps loss. When method killed garalon on HC they had one of he's front legs alive for the entire fight only taking damage from boss->leg cleave, this is only to say you dont need all 4 down all the time for him to be kited.
Again, it's only useful if you can stand in the circles. If not, your melee (who have to be in the circles to DPS the legs anyway) may run out of legs to hit, which will reduce overall raid damage. If you only care about topping the meter, DPS whatever you want, but focusing a leg will reduce the overall raid DPS unless you can stand in the circle.
As for being "too slow", I've never had a range issue. You should be staggering your kite double-wide anyway, which even with 4 down keeps him in range.
---------- Post added 2012-11-29 at 11:03 AM ----------
Originally Posted by Delabus
Use cooldowns on the legs then combustion it and spread but make sure not to refresh the dots on the boss with weaker ones when you swap to him
This has been hotfixed. Your DoTs on the leg are only stronger on the leg. They return to normal after a spread.
There are only 2 times that having all dps on legs, or nearly all dps on legs matter, thats when boss is under a certain % of hp where killing all remaining legs would kill it, and on start to slow the boss down