That’s like asking can you avoid using Chaos Bolt as Destro
The answer is yes, but why would you want to.
That’s kind of like playing ret paladin without templar’s verdict / divine storm.
Or playing feral druid without ferocious bite …
Not having Malefic Rapture in your toolkit may not be ideal or “viable” — but it’s not really a problem that the class spec wouldn’t be, without that spell in their utility. 
Personally, on my warlock I quite rather like Malefic Rapture — It makes me feel like I’m shattering the cosmos, using my applied afflictions as runes to bring about the incantation to its fullest potential. The spec feels a lot more fun.
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