While Dialga may have not gotten the best treatment (outclassed by Metagross and the Big 4 Dragons for both typings) would it be good for ultra league with DT/IH as a counter to Giratina?
Just my opinion but I think Dialgas stats are skewed too offensively such that it is very weak at 2500CP.
In masters it should win the dragon breath slugfest against giratina but there are more threats there in masters too. The good news is groudon is the only real answer to it, but is not an uncommon sight.
Dialga's typing allows it to beat both Giratina AND Lugia, aswell as take on other Dragon types. Dragon Breath/Iron Head will also be very spammable. While it will have to watch out for Groudon, and the potential Earthquake Metagross, there's no doubt in my mind that Dialga will be very useful in Master League PvP.
Ultra League is still up for debate, though. Dialga's high Attack stat doesn't do it many favors there, and while it will still beat Lugia, it will likely struggle against Giratina and Cresselia. It also has to fear Machamp.
