Well as far as porygon z goes, although hyper beam hits like a nuke, I perfer tri-atack. Well, is there anything particularly special you like about togekiss or arceus that made you pick em?
Oh yeah, I prefer Hyper Beam 'cause you can make it OP with only a few Nasty Plots (You can of course make Tri Attack more powerful but Hyper Beam is the powerhouse here). And Zap Cannon is very useful too.
As for Togekiss, it is a decent Pokémon. It has a low Move-Set, but the moves that it learns are all awesome. They're pretty much all you need already for going on a Pokémon League challenge alone. I, when I train, usually avoid teaching it Physical Moves (Except for ExtremeSpeed), mainly because it's not very good at them. ALSO, being a Tank is a huge plus to this. Being able to take hits from Pokémon such as Garchomp (Strong and fast, and comes from the same generation) is quite rare. To do this, the defender can't just be any tank. It should be a good tank. Other than that, if your Togekiss has Super Luck then it's a whole lot better.
About Arceus, (I have no reason for this) I seriously don't know. Although most Normal-Types were cool, I just didn't think of anything else to pick.