This is a bloodboil macro I have had kicking around for a while but never got around to putting up here. More generically, it can be used for any situation that requires you to mark three groups in a cycle.
What it does is, on the first press, puts raid symbols (the first five) on each person in group 2, then on subsequent presses moves the raid symbols to people in group 3, then 4, then back to 2, then 3, then 4, etc etc. Basically, hit it every time a bloodboil happens and it'll do the marking for you. If you don't want it to be 2-3-4, but rather 1-2-3 or 3-4-5 or what have you, you can change the '+2' bit in the first assignment up or down respectively.
/script
bbgn=mod((bbgn or 1)-1,3)+2;
local t = 1;
for i=1,40 do
local _,_,g = GetRaidRosterInfo(i);
if g==bbgn then
SetRaidTarget("raid"..i,t);
t=t+1;
end
end
SendChatMessage("Bloodboil Group "..bbgn,"RAID_WARNING");
Hopefully someone finds this helpful.