None of the cards you listed are "Broken" and you also didnt list how you think they are broken either... I'll list what I think of each.
Holon's Castform is just Holon's Trode/Magneton. I dont know why they reprinted it really. Not very good at all, unless you're short on Holon's Mag/Trode... Sure C for drawing 6 cards if you have 6 Deltas in play is good but when is that gonna happen? Giant Stump also ruins this...
Gyarados-d is one of those few good cards which I was talking about. According to the translation, the Poke-body is cumulative. So you have 4 Gyarados in play, then that's +40 damage for every attack for each Delta pokemon - great!
Pidgeot-d is quite Meh really. Why bother putting in Pidgeot-d when it counter's Pidgeot FR/LG. You may as well HAVE Pidgeot FR/LG in your deck to start with since the line is there. It may stop things like Magcargo too but it also disadvantages you unless you are running a Whole Delta Deck. Turning off anything that isnt a Delta can be good but will affect you in the long run.
Flygon-d is also one of the good cards in this set. Not only can it self attach energy but it is a Metal pokemon which can get past things like Metal energy, Scizor ex, etc. Flygon-d is a very good card but nowhere near broken. I count Flygon-d as the best card in this set.
Chimecho-d is also a Meh card. Not really that good. You can only search for the energy when there is a Holon's Supporter in play. People dont pack their decks with Holon Supporters. People commonly use Farmer and Mentor, but in small numbers. This also wouldnt be a good card early game.
Armaldo-d is a decent card. Flygon-d is better but this is reasonably good. If you run a low Supporter deck, then this card would be very good since 70 for MC is great. Fossil Smash for FCC is also good when discarding a fossil card. 3 Retreat is a bit much though. I would count this as the 2nd best card in this set.
That's what I think of each of those. None are really "Broken", yet some are reasonably alright. Compared to things like Cradily and Dustox ex, these pokemon get owned.