I'm currently boosting a hunter with a 70 tankadin and wanted to share my experiences as I progress. My plan is to do 100% instance boosting with this toon until he catches up with my shaman at 52. I'll then three box the 70 pally, shaman and hunter together.

Here is the path I've taken so far:

1-10: Quests. I stayed in Kharanos until I hit 10 and did my pet training. Then I took the tram to SM and headed straight to DM

10-15: Deadmines. It took a few runs and a few levels to get the efficiency down. Early on, I died a lot from the pather sneaking up on my lowbie. What I found is that the best way to deal with this is to move along through the instance as fast as possible. The pathers would finally catch up to me right before I entered the VC room so I would just hang out for a minute and kill them. I was getting roughly 8 bubbles per clear and I was clearing the instance somewhere between 10-15 minutes. I did hit the reset limit a few times.

15-20: Stockades. I really love this place for the simple fact it's in Stormwind making vendor / repair / rested area access so much easier. I typically three pulled the instance. First the straight hallway, then the left wing and finally, the right wing with the bosses. I tried single pulling the hallway and the left wing but it was too sketchy. The knockdowns make things a little hairy and it wasn't worth it, imo. Speaking of which, the knockdowns are probably the most annoying thing ever. I may load up on Free Action Potions next time I boost in there. All and all though, it went really smooth and I got about 1/4 a level per clear in about the same 10-15 minute window.

20-21: Scarlet Monastery. I made the loooong and deadly walk to SM, picked up the flight points on the way, honored the flame in each town and got several discoveries. This got me well into the next level. However, when I started clearing graveyard, I noticed I got the same xp / mob in SM as I was getting in Stocks. I noted that xp rate was slower in SM because of the level difference penalty. So I decided to hearth back to SM and do some more stocks.

21-25: Stockades. I'm baaaackkk. Really this seemed like the best move here. I had stocks down to a mindless science (watched TV while doing this) and just grinded out to 25. It didn't take long and I was able to pick up the kill quest at level 22 from the guy right outside the instance. (Note, there is also a Stocks quest giver in Old Town to collect 10 red bandanas that's worth picking up too).

25-27: Scarlet Monastery. I headed back to Scarlet Monastery and was getting MUCH better xp / mob. Almost double than before. I cleared Graveyard, Cathedral and Armory twice and dinged 27 (I think I was close to 26 when I left SW).

And that's it so far. At level 27 I'm close to 19 hours /played and there was a lot of BS time in there. My current plan is to stay in SM until 35 and then head to ST.

One other note, I had a friend bring his lowbie druid for 5 or 6 levels in stocks and was getting group bonus for about 10 extra xp / mob.