Short answer: IMO, get it.

Long answer: Minigun can be good. I got it in the same ECR and I'm enjoying it so far at the 2.5k SP level. It needs a unique play style which is what makes it fun. Honestly, getting it for just a few hundred thousand credits is what makes it tempting. And the ECR probability is better than normal. I got it in just a few spins.

One thing you'll eventually want though is the recoil implant. If you don't win it in the specialisation spree, you can buy the epic one for 600 acoins. It's steep, but worth it. Without it, beyond 30+ meters the wide hit cone causes a big damage drop off, and at this SP Guardian is a big concern so you want to stay out of its range. If Guardian crashes you, the minigun reload time is excruciating :-).