As a 10-boxer, I haven't had any trouble soloing any of the following:
(and I run most of them multiple times each week since I have four 10-box teams):
Classic
Molten Core
Blackwing Lair
Runis of Ahn'Qiraj
Burning Crusade
Karazhan
Gruul's Lair
Magtheridon's Lair
The Eye
Serpentshire Cavern (though help of Lay Vashj is helpful)
Mount Hyjal
Black Temple
Sunwell
Wrath
Naxx25 (except for KT - only attempted him solo once)
Eye of Eternity10
Ulduar10 + all hard modes (except Yogg - he requires a bit of help from friendly guildies)
ICC10 (except Lich King)
Cataclysm
BWD - just Omnitron Defense, since it drops some druid shoulders for one of my xmog sets
Transmogrification is a boxer's dream.
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