WowAce

What steps will reproduce the problem?
1. Fight Blood-Queen Lana'thel 25 (didn't test 10-player version)
2. Upon 3rd or 4th Bite-Round (can't remember exactly) the Addon starts spamming the chat-frame

What is the expected output? What do you see instead?
Actual output: You have attempted too many group actions in a short period of time.  Please wait momentarily before attempting further group actions.
Expected output: None, except for Raid Icons.

What version of the product are you using?
Latest Beta (r48-beta)

Do you have an error log of what happened?
See title.

Please provide any additional information below.

You're using a repeating AceTimer with a default polling frequency of 1 second. The function the Timer executes:
function Vamp:OnTimer()
    -- Set raid marks
    for mark, player in pairs(marks) do
        if player ~= "" then
            SetRaidTarget(player, mark)
        end
    end
end

This function is called every second and tries to set 8 raidicons in the last wave of bites, resulting in 8 actions per second.

My proposed (untested though) fix:
function Vamp:OnTimer()
    -- Set raid marks
    for mark, player in pairs(marks) do
        if player ~= "" then
+            local picon = GetRaidTargetIndex(player)
+            if picon ~= mark then
                SetRaidTarget(player, mark)
+            end
        end
    end
end

Only set the icon if it's not already set or if it's different from what it should be :D

Haha, thanks very much for this. I'm new to boss add-ons and wasn't aware there was a limit on marking speed. Your proposed solution looks great. Do you know if setting 8 icons at one time (the initial set) will be a problem?

Hopefully fixed in r50-beta. We're still setting all 8 marks on the 8->16 transition mostly at one time, and I'm not sure if the game will let us set 8 marks at once. If not, I need to know how many it will allow, and add a manual throttle.