How many people have 6 titans? They are supposed to be rare cards, so unless you are one of those cheaters, that combo is rarely manageable.
Not only is rarity is not involved in card balancing, but a lot of people have 6 titans. Try playing T50 with a couple of these farms up. You will have six in just one day. By the way, rarity has nothing to do with card balancing because cards should be used at their full potential. It is better to have a card underpowered for some people and balanced for others than a card extremely overpowered for some people and balanced for others.
Armagio is rather quickly killed easily these days. Even if Armagio is still alive, its HP gets reduced quite a bit in just one turn.
I hope you realize that Armagio has the option to use gravity pull. If you don't gravity pull your armagio, how do you plan on killing it? And if you played, say, 5 lightnings on it, it would be a huge waste.
It's probably not so much what is "wrong" with this card but rather other cards/decks have been becoming increasingly powerful that catapult is left behind.
Since catapult was released, 4 new cards have been in development. One of these is a huge buff for gravity, which increases the options to use catapult.
If a card is only useful when combined with a bunch of rare cards and upgraded cards, that is hardly a good card.
I have no idea where you pulled out upgraded cards, but I already said why rarity should not effect balancing.
Try using this in unupped decks for instance. No wonder nobody is using it.
It works fine in the right unupped deck. It is not used as much as it should be because one of the strongest combos with it involves rares.
EDIT: By the way, I don't understand the poll option, "Allow it to target creatures too." Catapult can target creatures.