i think u dont see the point
15-59 Randomdungeons [RaF] runs smooth
but when the bot is Starting BC it dies ALOT specially in Hellfire Ramparts and The Blood Furnace (even worse since WoD started) cause of missing gear
to avoid that its very good to farm some of the "highlevel" Classic Instances (btw who told you Farm option is only for Highlevel thats total bullshit)
So if the bots start running BC with level 61 and a better gear it running smoother less death and u save time even if its not so effectiv to farm the classic dungeons for EXP
And trust me i leveled many charakters with RaF and thats the most stressfree way
I am happy you have experience with Dungeonbuddy already.
As
DrDoctor mentioned, do use all looting under personal or group loot, so the toons get some green gear off the trash mobs, which combined with the quest rewards items, obtainable from the quests, deliver nice boost to the whole 5man group.
Then consider choosing optimal healer/tank class for the group, some classes starve at low levels since 6.0, others are nicely buffed, so you will face troubles less in the 15-90 pace.
The most problems I have seen since 6.0 in past 69, then past 79 - the 59-60 transition is not so dramatical, like these mentioned before.
Since the most parties starve of gear in these breakpoints, consider a small 30min brake on them, then for example on lvl 80 use Kicks questing or manually fly to Hyjal for couple of minutes to buy some missing parts of gear from the quartermaster there. But if you do have some heirlooms, that is usually not needed.