What's this about ho-oh being bad in ubers. With Groudon support and his impressive speed/atk, almost nothing except Palkia and Kyogre can switch in safely, and if they get burned the pain is going to be all the more for tham added onto the already good damage done.
Here's some calcs. I'll use the generic standard EV spreads. This is assuming you use shoddy and have your ho-oh with 31 atk EV's. If it's wifi, My ho-oh has 29 so no biggie. All of these using Metalkid's Calculator.
Ho-oh w/Max atk(394) Sacred Fire vs. 6hp/0def Dialga Neutral Nature Under sun=68.13% - 80.12%
Same stats Ho-oh vs. 240 hp/16 def Dialga Neutral Nature=57.36% - 67.33% still a 2HKO
Same vs. Max/Max Giratina +nature Under sun=17.26% - 20.24% (Considering Giratina can't Burn Ho-oh like it would say, Swords Dance Arceus, it can't really do much more back)
Same vs. Max/Max Blissey w/+nature under sun= 68.81% - 76.1% (making him a great switch in to CM Bliss that come in to ruin your SpecsTwo's fun)
Same vs. Max/Max Skarmory w/+nature under sun=62.28% - 73.35%
Same vs. 36hp/0def Rayquaza w/neutral nature under sun=41.11% - 48.61% (and hope it doesn't get burned)
I could go on. Throw a choice band/Life Orb into the mix and he can really lay the hurt down.
Three generally seen ubers switch into this safely-Palkia, Kyogre, and Giratina. Everything else is potentially 2HKO. And Unlike the prior two, Giratina can't do anything back since it can't burn ho-oh obviously, and it's defenses are nothing to laugh at.
Two things to note, one is that yes, many other ubers can do similar damage calcs with their STAB moves, but none of them threaten to Burn 50 % of the time, thereby keeping any physical attackes scared to death for that switch in. Also, is the 4x stealth rock weakness. Donphan and Forretress remedy this quite well, since clearing the field is also a pretty big priority for rayquaza sweeps, it's pretty good in combination.
In short, with Groudon and Rapid Spin Support, Ho-oh owns. Kyogre and palkia both share a common coutner in the form of a Defensive Latias, and ho-oh can easily come in on anything meant to wall in the uber metagame (especially really fat eggs).
Don't underestimate ho-oh, or you'll likely be swept by one.