Done this several times and never noticed this. The TOV portion for 4.0 is just brutal takes 2 - 3 days of clearing to get all the drake parts if you're lucky.
Charm 5.0 head in to Sleepers and usually can get everything in the first room if not always will get one toon done in a full trash mob clear.
Just looked on the clone drake parts are 1.25% drop chance.
Strange Metal, Strange Ice, Essence of Treachery and All-Seeing eye are 2.5% drop chance.
Would you kindly consider bumping the drake parts up to 2.5%?
I know this will be an undertaking as every trash mob will need to have loot tables updated, as an alternative to trash mobs could the named loot mobs add drake parts to them as a 10% drop chance? It would give some of us a reason to actually kill them when doing this quest.