Well all my team have the heirloom shoulders and chest pieces, but they only give kill XP ? So with the very small xp gained from killing stuff removing the higher toons heirlooms would probably not help a great deal.
I have done a little bit of running them in UK with my 80 druid but it is relatively slow going.
On my server AV queues are about 30 minutes.
I did think about running just the 3 lowbie toons through UK but unfortunately my main tank is on the same account as my lowbie tank and so I have no high level tank to run with the group. I did consider just running my lock with my druid in his tanking gear to help clear mobs faster but I am not sure how big of a hit my lowbies will take in XP vs the speed I clear the run at. Heals for my druid in his tanking gear might also be an issue but that would really only be on the boss fights (druid is normally resto)