Alekhine's defense isn't dubious. It's a reasonable choice.
Is it good for the 1400 level in particular... umm... it wouldn't be my first choice because white has a lot of options, and it's more of a counter-punch opening (so you have to absorb some white initiative first)... but having said that, it's not so bad.
I'm rated around 1450 in Rapid and I'm interested in learning the Alekhine's Defense. I'm currently playing the Najdorf against e4 and I like the tactical, complex positions that arise from it, but I want to try something new because why not; thus, the Alekhine. It's supposed to be aggressive, and it's way less common than the Najdorf which means I can surprise a lot of opponents. Do you think it's good at my level since many players with the white pieces won't have faced the opening that often, or do you think it's too dubious to give up so much space and central control?