So as noted before i am running shaman+4 warriors and here is my experience so far:

I feel this team is very fast leveling and my instance running has been a net positive thus far (lvl 21 currently)

I started Instances at lvl 12 with RFC and stayed until 16. I only cleared a portion of the instance at first but once i hit 14 i was clearing most of it. At 16 i went to WC and same ordeal only cleared the lower level portion until 17-18. I always kept my warriors in full "of the bear" gear and shaman in "of the eagle" fairly cheap to snag on the AH.

I mainly pull with the shaman back to the warriors so not to pull extra packs of mobs. Now at 21 i can take on 4-6 mobs(in WC) before the shamans mana bar is depleted.

I did the quest for https://classic.wowhead.com/item=6505/crescent-staff as soon as i could and has made a big difference in clear speed.

I am currently at 1d 14 hrs played on this team. Not sure how fast that is but doesn't feel entirely horrid to me. I cant wait until windfury totem.

Oh and healing is fine with the shaman just laying out healing waves. I just got lesser healing wave at 20 for when i do accidentally over pull. So far hardest mob is last boss of WC he takes half my HP bar in 1 hit but still able to down him with minimal casualties.

Maybe i can throw together a short video if needed.