I agree with you 100%, but I think you are not considering a few things.
1)New players usually don't and shouldn't be power leveling. This leads to new players in raids like the shroud with out the proper equipment. Then Vets come to the forms posting thread complaining about noobs in their raids. Telling new players to buy Delera's first then use it to power level and pickup other packs as they come on sale is doing everyone a disservice .
2) Anyone familiar enough with the game with the ability/want to power level wouldn't bother posting a thread asking which packs to buy.
As Tumarek has said it is far more important to have other packs before Delera's.
But, if you want to power level and are not concerned with what you will be doing at end game Delera's is a must have.