I'd say that Sazandorah's inability to have both Dark Pulse and Earth Power at the same time is fairly trivial, as I believe that both Earth Power and Surf on this Pokémon are fairly outclassed by Focus Blast, which can hit Heatran (one of, if not the most important Pokémon which Earth Power/Surf/Focus Blast is intended to hit, since nothing else resists the combination of Draco Meteor and a Fire-type move. In fact, as a result of this, it becomes even more obvious that Earth Power on Sazandorah is quite useless compared to Surf and especially Focus Blast, since Balloon is by far Heatran's most commonly-held item) hard, while at the same time being able to inflict heavy damage upon Empoleon (just like Earth Power can), Porygon2 (an extremely tough Pokémon to beat in this generation), and most importantly, being able to deal massive damage to Tyranitar (one of the most common Pokémon which switches into Sazandorah, and a Pokémon which laughs at Earth Power, Surf and Draco Meteor due to Sandstorm increasing its Special Defense), if not KO it outright.
As for Shandera, it is destroyed by Dark Pulse. Also, speaking of that Pokémon, something which seems to work is switching Sazandorah into a Shandera after it just revenge-killed one of your Pokémon with Shadow Ball or a Fire move, and then selecting either Flamethrower or Focus Blast and watching as their Nattorei/Forretress/Tyranitar gets obliterated on the switch. Fun and effective indeed.