Question for people who play Shaymin in EX decks.

I've seen loads of decks in the current meta lists that run multiple EX mons plus Shaymin for support. I've tried running them, with both versions of Shaymin, and I have found that I lose because I open with only Shaymin in my hand (either because it dies or I just lose momentum building a useful mon) FAR more often than I win because of anything useful either of its abilities do.

What am I missing here? Like in a Dialga deck specifically, the energy it generates makes the 1 less retreat feel mostly useless, and the 10 HP heal from the other rarely seems to actually make the difference in a game. Feels like if I'm going to run an EX heavy deck, I should always have a game condition that forces the opponent to take out two EX mons instead of just one EX mon and the chance to easily pick off Shaymin.