I know this is heresy, but count me in the scale+banded crowd for Sedna. Here's my logic:
*LOGIC*
1. Fair enough if that's the role you're taking. It's pretty defensive, the early levels are great for nabbing kills as Sedna before people start slow stacking and you're missing out on that because your entire arsenal consists of health and armor...which doesn't help you push people away very much. Monks give you dps and healing for free, I'd say thats more versatile than health and armor. You already have BotF, more health isn't needed at that point, but you can still only cast 2 heals in early game.
If you take a lane by yourself, fine stack hp that much if you think it works. I take lanes in a pair so I need to be able to heal an ally as well, which drains mana horribly in the early stages. Monks help with this because they can generally account for random fire that hits me, while my ally takes most of the heat and I heal him.
2. You can rely on them as much as you can rely on your own heal. Monks heal you while your being grasped (which you would know happens quite a lot). They also heal you whether you have mana or not.
3. They most certainly are xp and gold farmable, just not as much as before. I still don't buy them immediately, I get the gold upgrade first, and the two tower ups. You can only be healed every 8 seconds, so this will be slower than if you had your own lvl2 or higher monks.
4. False. They apply different debuffs.
Monks
if Buff.HasBuff(target, 'HighPriest01HealCooldown01')
Buff.ApplyBuff(heal, priestBuff, unit)
Buff.ApplyBuff(heal, 'HighPriest01HealCooldown01', unit)
Clerics
if Buff.HasBuff(target, 'HighPriest02HealCooldown01')
Buff.ApplyBuff(heal, priestBuff, unit)
Buff.ApplyBuff(heal, 'HighPriest02HealCooldown01', unit)
5. So sell your priests in midgame if you think they're poor at that point. I'll keep mine because they force my opponent to remove them before they can get to me. None of the AoE spells kill them in a single swipe, so as part of a creep wave they'll survive quite nicely, and if they die you can resummon for instant heals.
6. Yep. Not sure why you'd need a speed build as Sedna though, it's not like you're a dps machine. There's better things you can be doing, like stacking mana so you can silence/heal/pounce spam.
I've started taking cloak of night/totem of revalation/monks for the start, I must say it's been pretty successful. People don't expect you to blink/pounce to nab them when they run at the start.