[SDPhantom]

From what I see of your code, it's much more complicated than it needs to be for what you describe. Essentially, too much class-style programming is going to end up bogging down the addon with tons of indexing operations. The example I'm going to show is written from scratch.

local HistoryData={};--     Stores data by index
local HistoryLookup={};--   Links indexed data by timestamp
 
local function OnUpdate(self)-- This will be used to update any shown info
    -- Make whatever calls you need here
 
    self:SetScript("OnUpdate",nil);--   Unregister this handler since we'll no longer need it for now
end
 
local EventFrame=CreateFrame("Frame");
EventFrame:RegisterEvent("COMBAT_LOG_EVENT_UNFILTERED");--  This event that isn't affected by filter settings
EventFrame:SetScript("OnEvent",function(self,event,timestamp,subevent,_,sourceguid,sourcename,_,_,destguid,destname,_,_,spellid,_,_,amount,over,absorb,crit,multi)
    if subevent=="SPELL_HEAL" and spellid==1064 and sourceguid==UnitGUID("player") then
        local hops=HistoryLookup[timestamp];--  Pull cast data from lookup table
        if not hops then--  If we didn't get any data, make a new entry
            hops={};--  New hop table
            table.insert(HistoryData,hops);--   Add to data collection
            HistoryLookup[timestamp]=hops;--    Assign a link to the same table to our lookup so we can grab it next time
        end
 
        table.insert(hops,{--   Add hop to hops table
            timestamp=timestamp;
            guid=destguid;
            name=destname;
            amount=amount;
            overheal=over;
            absorbed=absorb;
            critical=crit;
            multistrike=multi;
        });
 
        self:SetScript("OnUpdate",OnUpdate);--  Register our OnUpdate handler to run after all of the events are done firing (unregisters itself when done)
    end
end);

This will end up populating the HistoryData table with instances of every single cast of Chain Heal. Every entry will contain a list of every hop the spell did between targets, including who those targets were, how much they were healed, crits, and multistrikes. I also added a little code to reliably run after the events all fire.

Originally Posted by jeruku sirann has a good idea but instead of an OnUpdate you could try a C_Timer.NewTicker.

That would run the callback function multiple times per cast (once for every hop recorded).