Collecting 20 of these for the secret phoenix pet is an impossible task with all the competition and two players alone can control the area so you likely won’t get the chance to tag a single elemental without standing still and camping a specific spot.
Either increase the drop rate or reduce the total amount needed because the queue of players interested in this stretches beyond next Cataclysm Timewalking.
If it were a drop from current expansion content with shared tagging system there would at least be a gameplay element to it, however there is nothing fun about one shotting mobs in a low level area for 5 hours straight (under ideal conditions).
This entire activity is outright insulting.