Some of my friends find fun in constantly leveling alts.
Altho i am especialy pvp oriented , i try to help them from time to time.
With this post I wanted to share my experiance in this field.

First 10 levels they better do themselfs - one solo kill is solid xp % at this time.
After that i start directly with RFC run for the quests and then go spamdo SFK until they hit 20.
After that SM cath directly until 34 for the sm quest. The speed is crazy , its around 1 level per 50min-1 hour.
If you get instance locked - you can try running 5x RFD but thats optional. In the usual case you wont be THAT fast
Around 37 you can start with uldaman , but 40 is ok as well.
Uldaman is pretty easy lately for me - i have 10.5k hp totaly unbuffed.
Mara is bad for aoeing , better start with brd , but there you should be slower - mobs hits for more.
Imp bliz works well here, but requires more attention to play and drains huge chunks of mana.

I found out that Arc/Fire works best for this level of dungeons (my usual spec is close to it anyway ) :

Talent Calculator - World of Warcraft

Mostly because two key talents - spell power and blazing speed.
First ensures that aoe dmg crits will be huge and blazing speed is key talent to get large crowd of mobs
FAST - before you get hit too much.

My spel rotation - i start with running towards the closest mob - hit rank 1 Arcane explossion just after i pass it , then run around spaming rank 1 AE or ice lance on closest mob of a linked pack. When i get around 10-15 mobs - collect them and frost nova them , then start Flamestrike.
Dont worry about spells or ranged attacks - 70% from burning soul .
After flamestrike hits with cone of cold + blastwave + spam 2-3 arcane explossions - everyones death.
Canibalise after that if you have enough mana.
Repeat.
Have the low lvls behnd you , be ready to ice lance any mob that they agro while you aoe. Watch their health -
if its not 100% then check whats going on with them.


A very usefull hint - group of 5 levels faster than agroup of 2 - group bonus is huge -
in sm cath its 33% of the exp they are getting when grouped with a lvl 70.
I usualy just post this in general zone chanel :
"I am gonna run SM cath plenty of times for a friend , anyone in this level range wants to tag along ? I have 2 free spots."
There is always people happy to come

Oki , posting there too.Thanks.
Whoever can - delete this thread , i cant do it myself.