We dont know when gen IV will come out, but never can be too prepared, any ideas what the raid bosses could be, or what rank they would be?
I think its certain Lucario and spiritomb and the three starters in any stage could be there, Garchomp doesn't seem likely, but other than the obvious?
I'm looking forward to Palkia and Dialga, probably in that order. Dialga, in particular, if it gets a reasonable Dragon double moveset, will be a very effective Dragon killer, and with a good double steel moveset could be the best Steel pokemon too, and possibly a good generalist as well. Giratina should be interesting, getting a really strong Ghost type.
About the non-legendary ones, I don't know. Never would have pegged Mawile or Absol as raid only. There might be a few of those, too.
Impossible to predict the non-legendary ones. Starters are likely but not certain, everything else is a wild guess. Work on obvious legendary counters (Machamp, Hariyama, Groudon, Kyogre, Ray/Nite/Sala, Gengar, Tyranitar, Mewtwo) and other than that, try to make a balanced roster of strong attackers against all types.
Thats what im trying to, but the gen 4 dragons tend to...throw a wrench in almost any possible counters (ie palkia only being weak to dragon and fairy, one of those weaknesses removed by dragons also being weak to palkia and fairies tend to be not good aside from the VERY rare gardevoir)
In all likelihood, Machamp wont be any use against dialga, given simply its monstrous defenses and high attack (on par with rayquaza), and golem's weak to steel.
I also started recently, so I dont have any legendaries other than the three birds (after the next breakthrough) ho-oh and lati's, none of the better ones
Palkia's top counters will be whatever are the best DPS dragons period. Against water moves they will be completely amazing and against dragon moves their DPS is still so much higher than anything else that they're the top choice. This is the exact same as with the Latis, where Ray/Dnite/Sala still make top 24 in TDO even against double dragon movesets and completely outrank everything else in DPS. And then you'll want Gardevoir and possibly Togekiss (if any reasonable moveset) if you want to tank the double dragon movesets instead of going for maximum damage.
As for Dialga, the high defense doesn't matter one bit, every attacker faces the same. Machamp currently has the highest DPS of all mons that can hit Dialga for super effective and that is what matters. The ground types (Groudon, Garchomp, Rhyperior, Mamoswine) are all strong contenders with high attack stats and lots of bulk, especially if they fix ground type moves to not be garbage. Mamoswine and Rhyperior suffer from a steel weakness but are so tanky they might still out-TDO Machamp.
I don't know why you mention Golem, it's not even remotely in consideration for a Dialga counter.
So if you don't have any previous legendaries, try to work on Dragonites(and Latios), Gardevoir, Machamps and also prepare for Togetic, Mamoswine and Rhyperior if you can. Meanwhile the Machamp army you should be building for Dialga will serve you extremely well in gym fights and if Regis become the next legendary raid bosses.
