you will rarely land 2 heads, even with fliptini. odds are just not in your favor. assumming you reroll everything that isn't double heads you have 43% chance of landing a heads, meaning you have less than 50% chance to OHKO all the primary threats currently (U-Necro and buzz), while they have a much easier time KO-ing you.
and to KO 210 hp poke you have less than 50% chance AND need a choice band. all for the modest price of 4 energy, because you can't even use DCE.
at that point i'd say it's simply better to play Ho-Oh, 180 guaranteed, 210 with CB, and has fighting resistance.