We were running some calcs earlier, and just as a forewarning, I wouldn't get too excited about Electivire. It is, quite frankly, a rather bad Pokemon. It's problem? Lack of high base power moves and middling special attack mean that, while often being able to hit the opponent super effectively, it can't OHKO even frail Pokemon. For the following calcs, I'm assuming a 4 Atk / 252 SAtk / 252 Spe spread with a boosting Speed nature, Life Orb, and the moves Thunderbolt, Flamethrower, HP Grass and Earthquake
252 SpA Life Orb Electivire Flamethrower vs. 4 HP / 0 SpD Sceptile: 237-281 (84 - 99.6%) -- guaranteed 2HKO
252 SpA Life Orb Electivire Thunderbolt vs. 0 HP / 4 SpD Zangoose: 231-274 (80.4 - 95.4%) -- guaranteed 2HKO
252 SpA Life Orb Electivire Thunderbolt vs. 0 HP / 4 SpD Sawk: 195-230 (67 - 79%) -- guaranteed 2HKO
252 SpA Life Orb Electivire Hidden Power Grass vs. 252 HP / 4 SpD Seismitoad: 348-411 (84 - 99.2%) -- guaranteed 2HKO after Leftovers recovery
And so it goes on. Earthquake would be used to hit Lanturn and Dragalge, otherwise common Pokemon that can easily eat up anything Electivire can throw at them. The fact is, while it's obviously stronger than Magmortar's it's still a 2HKO, just like its fiery counterpart. Magmortar can also actually OHKO stuff thanks to its more useful STAB in Fire Blast, and stronger coverage moves. The lack of Speed is notable, however, it outspeeds what it needs to, as it's supposed to be a wallbreaker. Just to compare, physically based Magmortar actually hits harder than specially based Electivire -.-
Going physically based with Electivire also isn't something I'd recommend, due to being hard walled by stuff like Seismitoad, Rhydon, Steelix, Tangela, and the list goes on. The problem is it just can't seem to OHKO things...
Edit @ Below: nice idea with using both together, but Electivire seems too slow to really use as a cleaner for me :/