Allright, just registered for this thread.
As far as I'm concerned those bosses ARE possible (with or without Void Star / T5, doesn't really matter)
Classic:
AQ 10 - complete
MC - complete
BWL - You'll need someone who kills the adds or uses the Dragon, otherwise soloable, all of the other bosses are possible (one of the Drakes is rather annoying though; you have to pass the aggro und build it up again so his Shadow Veil won't heal him all the time)
AQ 40: All bosses except C'thun (due to mechanics) are possible. Haven't tried Viscidus yet, but I just got my new Frost Damage Wand ... I'll edit it in later. As for the Twin Emperors: It's a VERY tricky fight and I haven't downed them yet but with the right positioning, macros for the emperors and a LOT of luck (once you pet gets a knockback in a wrong direction you're basically screwed) ... but still doable
BC:
10-man: Karazhan + Zul'aman no problem at all.
25-man: Maghteridon is doable, Gruul is easy as well. High King Maulgar can be a bit of a nuisance (I hate Death Coil. I'm looking at you, damn Warlock-Ogre-dude!)
SSC: Hydros is doable, Lurker no problem at all, the Demon Hunter is a little bit tricky but downed him the second try after realizing his Chaos Bolt Debuff thingies have a limited range (Demonic Circle ftw!), Karathress should be doable - has been done iirc, as well as the Water Giant ... Morgrim or something? Vashj is IMPOSSIBLE due to the mechanics with the stones ... and also all those damn adds. I hate them.
Tempest Keep: Complete. Al'ar is no problem, Void Reaver is just a 'Keep Moving' Fight and I never had any problems with Solarian. Kael'thas is rather annonying, as well. The hard part is killing all of the Advisors at once, still dieing a lot on those.
Black Temple: First Boss is impossible ... well he would be possible if you'd be able to burn him down with ~45000 DPS during the cooldown of his Shield. Doesn't target you with the spike but the shield'll go up nonetheless. :< Some of the other bosses are doable as well - the Giant Infernal thing, Akama and a few others. Afaik, the Reliquary, Gurtogg and the Council are impossible. Illidan is doable.
Hyjal: Except the fourth boss (Doom Spell - instant death after 1 Minute) completely doable.
Sunwell: (How I love thee! <3) Kalecgos isn't doable due to the mechanics, Brutallus is probably too hard right now (Armor Reduce + Meteorites), but I guess he'll be no problem in a Tier or two. Felmyst should be doable, the Twin Eredars should be as well ... I think. Not so sure about M'uru, but Kil'Jaeden has been done already (and I'll try it as well. )
WotLK: (I'll just count those I know have been downed already or those I think can be downed)
- Archavon (I hate your Grip.)
- As already mentioned some parts of Naxx 10 / (25?), Sapphiron is no problem at all and I'm still wiping on Kel'Thuzad but he'll go down eventually!
- Sartharion
- Most of Ulduar, iirc
Excuse my mistakes, english ain't my mother tongue :3