Recommended PROFILE and class -
Orc Hunter (long term, see below) or Blood Elf Mage (1-10).
Questing Bot I use
Kick's Mega Profile 1-90 Pack(Horde)... which whilst is the most complete questing profile, requires a lot of monitoring. I have botted [to] an 85 Blood Elf Warlock (great experience, Demonology very powerful for bot levelling), Blood Elf Hunter 70 (pure pleasure to level as a bot -use fpsware's CC!), an 81 Orc Shaman (slowest, in my experience -relatively poor CC's available, and Northrend botting prior to Sholzar Basin sucks --in my opinion) and a lot of fishing with my 90 Monk. I'm currently botting 3 accounts including a 38 Undead mage -who had problems straight away from the starter zone, second quest in.. grrr... but few problems since.
Bugs - There are too many QuestBehaviour bugouts and FlightPath issues (in my experience) for me to agree that 'long sessions' (5+ hours) of botting can be done reliably, at least questing. If you do find a good profile, stick to it --that is one, once started can give you quests/hour without monitoring. Quests/hour do increase at later stages, but require more supervision (think of funky Outland bombing missions, Northrend geography and circumventing Wintergrasp fly zone...).
Solution - The trick is to finding the starter zone that does not bug for you, so that you can roll it repeatedly. My recommendation is to try each race's starting zone, as a hunter or warlock if possible (definitely ranged) and see what seems smoothest. Use TitanPanel addon with the XP plugin to monitor XP/Hour and compare your progress.
BOAS -I don't believe these increase your Guild XP/hour (quests/hour) that much. I have characters botting with full BOAs and one with starter gear; they both complete around the same XP and Guild XP because of the bug issues. It's just that way. In dungeons, when I play them myself, BOAs faceroll everything and are very powerful -as they are in quests -but for botting purposes, I would not recommend going out of your way to deck your bots out in BOAs. Nice if you have them already, though.