One could ask the same question regarding AV reward gear. One can acquire honor gear…none of it can be equipped until level 80. Now if one could run ToC normal with a “normal” group of say 77…then I would see a valid argument. Just because I can take my 80 <insert class here> and run a group of level 20’s through say Scarlet Monastery and gear them all up with level 40 gear,doesnt make the system flawed.
Heroics have a barrier to entry. BC it was faction, and WoTLK is level restriction.