DS Solution

    importantSpellList = {
        [1776]    = true,           -- Polymorph
        [61305]   = true,           -- Polymorph: Black Cat
        [28272]   = true,           -- Polymorph: Pig
        [61721]   = true,           -- Polymorph: Rabbit
        [61780]   = true,           -- Polymorph: Turkey
        [28271]   = true,           -- Polymorph: Turtle
        [605]     = true,           -- Mind Control
        [33786]   = true,           -- Cyclone
        [1513]    = true,           -- Scare Beast
        [113506]  = true,                   -- sCyclone
        [51514]   = true,           -- Hex
        [5782]    = true,           -- Fear
        [34914]   = true,           -- Vampiric Touch
        [116858]  = true,           -- Chaos Bolt
        [20066]   = true,           -- Repantance
        [115750]  = true,           -- Blinding Light
        [145067]  = true,           -- Turn Evil
        [10326]   = true            -- Turn Evil
    }

for i=1, #ArenaTargets do -- Checks every Target...

    if LineOfSightCheck() then -- ...If current Enemy is in LOS...
        local spellName, _, _, _, _, endCast, _, _, _ = UnitCastingInfo(Arena..i)

        if spellName ~= nil then -- ... and if current Enemy is casting something....

            for key, value in pairs(importantSpellList) do -- ... it Goes through the important spell Table ...

                if GetSpellInfo(key) == spellName then -- If the current casted Spell in the "IMPORTANT LIST"...
                    if ( (endCast/1000) - GetTime() ) < 1 then -- ... Cast DS wehen remaining cast time is <1 seconds
                        castThisSpell(GetSpellInfo(77606),Arena..i)
                        return true
                    else
                        return true
                    end
                end
            end
        end
    end
end