I feel like with Assault Vest Ho-Oh becomes a little too much of a jack of all trades. Its special bulk becomes incredible, but without Roost it cannot take advantage of this to become a proper wall; it is forced out as it gets worn down. The loss of Leftovers also hurts its defensive capability considerably (although this is in ways compensated by the Assault Vest). Offensively, without Life Orb or Choice Band it still has respectable power, but is far less devastating and begins to have numerous solid switch ins.
There's also the matter of Ho-Oh really having no good 4th attacking move. Sacred Fire, Brave Bird and Earthquake will hit essentially everything viable in Ubers hard enough, especially since STAB Brave Bird hits harder unresisted than many super effective coverage moves (and Sacred Fire in the sun even more so). Flame Charge is nice, but the purpose of Flame Charge is to capitalize on the immense offensive threat Ho-Oh presents when one of its main flaws (its middling speed) is removed, and such sets would be far better served with Life Orb to get as many OHKOs as possible. Flame Charge is also usually outclassed by Tailwind; Tailwind remains effective with far less speed investment allowing Ho-Oh to be bulkier, allows Ho-Oh to outspeed more threats and can often support the team if Ho-Oh is forced out within a few turns (as it likely will be - if not, it will probably have caused enough damage to ensure a victory).
There's also the matter of Ho-Oh really having no good 4th attacking move. Sacred Fire, Brave Bird and Earthquake will hit essentially everything viable in Ubers hard enough, especially since STAB Brave Bird hits harder unresisted than many super effective coverage moves (and Sacred Fire in the sun even more so). Flame Charge is nice, but the purpose of Flame Charge is to capitalize on the immense offensive threat Ho-Oh presents when one of its main flaws (its middling speed) is removed, and such sets would be far better served with Life Orb to get as many OHKOs as possible. Flame Charge is also usually outclassed by Tailwind; Tailwind remains effective with far less speed investment allowing Ho-Oh to be bulkier, allows Ho-Oh to outspeed more threats and can often support the team if Ho-Oh is forced out within a few turns (as it likely will be - if not, it will probably have caused enough damage to ensure a victory).
