Thats is why i have a choice scarf palkia to kill ho oh.
This is a mistake I feel a lot of newer players make. The thing to keep in mind when building a team regarding a certain threat is how easily your team (in general) gives it free turns (meaning, where it has opportunities to throw out attacks without risk to itself) and how well you can switch into that Pokemon and regain momentum (by forcing the threat out). The issue Hack brings up with your set is that it gives Ho-Oh numerous free turns, it can switch in directly on your Steel Arceus under just about any conditions. Because Ho-Oh is such a large offensive threat this is a major problem because it is difficult to add members to your team that can repeatedly switch directly into Ho-Oh (which you would need because Ho-Oh can come in easily multiple times throughout the game). The problem with relying on Choice Scarf Palkia to solve this issue is that Palkia struggles immensely to directly switch-in. Eveen if you have perfect, god-like prediction, Choice Scarf Palkia isn't even sure to force Ho-Oh out as there may be conditions (such as Sun) where Ho-Oh can actually afford to stay in. Even if you do manage to force Ho-Oh out, Choice Scarf Palkia doesn't put much pressure on the opponent's team which means you'll gain very little from it.
To sum it up, your opponent will have: Multiple turns to bring in Ho-Oh and do what he likes + be able to put large amounts of pressure on your team, essentially taking a kill everytime it comes in. (you only have 6 guys on a team)
On the other hand all you have is: A check (Scarf Palkia) that can not easily switch into Ho-Oh the many times Ho-Oh will switch in + be unable to apply much pressure on the opposing team every time your Palkia miraculously does come in.
As you can see, your opponent is at a heavy advantage.
Now, you basically have two options to fix this:
A)
Limit the number of free turns you give a specific threat.
This means running Stone Edge on Steelceus.
B)
Be able to switch into the specific threat as often as it can switch into you.
This means running something like Carbink who can easily be spammed on the majority of Ho-Oh variants.
Keep in mind option B isn't as effective as option A, especially when using something like Carbink, because you are reacting to your opponent. This means that it is more likely your opponent will hax you before you hax them which can heavily turn the game in their favor. On top of this, hard counters like Carbink don't apply much pressure themselves so you still come off with the lesser deal. An alternative counter that could be as dangerous as the opposing HO-Oh would be effective (like Phys Def Ho-Oh) but these either don't exist or are situational.