Both Pokemon were made for attacking, not defending. Even with Eviolite's boosts, Electabuzz is still frail. 65 / 57 / 85 defences are nothing impressive as opposed to it's 83 / 95 / 105 attacking stats and Speed. Electivire however is gifted with a 123 Attack stat, 95 Speed and an excellent move in Wild Charge to complement it.
Eviolite should only be used on defensive Pokemon, like Chansey or Dusclops. And Electabuzz has no interest in being bulky. With Eviolite out of the question, the only thing separating the two are their Speed stat, which Electabuzz is better than Electivire in. However, in a tier like RU, 95 Speed is nothing bad, and Electabuzz stands outclassed by it's older brother.