All in all, Dialga still post impressive game performance the best being sublime base 150 Special Attack.
Deoxys is perhaps one of the flexible of all legendary; he assumes any role depending on the form it comes by.
With forms that excel in the attack, defense and speed and this support the reason why Deoxys is considered one of the best legendary Pokémon.
The discovery of Primal Reversion has been a real blessing to Groudon. When its transition into its primal form this thing becomes a whole different giant or beast.