So called gig speed

Just had newly installed Gigabit Internet yesterday. The same day I got the Arris Cable Modem SAB 8200  just for it since my old one didn't support the docsis 3.1 standard. After it was all freshly installed, I was only getting speeds between the 200s and barely into the 300s on my wifi. Tech said that he had called the issue in to Xfinity and some other techs would be working on the issue on Xfinity's end. He also said that it should take between 1 - 2 hours for the issue to be fixed, but that another tech would come to my house before the end of the day to  double check the line outside my house and confirm I'm getting the speed I should have. Well obviously it's now way past the end of yesterday and today is a brand new day for me to wake up to just to experience the same ole bad speeds and service! Hurray... -.- Anyways, now I'm having to wait until tomorrow...the next day until someone even comes out here to check the problem the tech left behind in his rush to get to the next job. Meanwhile, I'm sitting here just a few inches from my Arris SAB 8200 modem and directly connected to it with a Cat6 Ethernet cable while only getting higher speeds between 550 Mbps and barely into the 600 Mbps range. 

I know that wifi speeds are on average signficantly lower than Ethernet speeds on any tier, including Gigabit Internet, but c'mon...barely the 300 Mbps range? I could understand if it was like between 400 Mbps and 500 something Mbps on my wifi connection but that's just simply not the case. And what's even more alarming is the speed I get when I'm even connected just a few inches away directly into the cable mode...550 or 600 Mbps is more of the kind of speed I should be experincing on Wifi shouldn't it?

I have had two techs checking everything and Comcast tech center has told me that issue is the Node as there is a moderate noise causing loss.  I have not been told when and if Comcast plans to fix the issue as I am paying for giga speed and I am getting a 500 MBS speed.  I doubut if this is lawful.

I would be happy and content if my wifi speed was just around between 400 Mbps and 500 Mbps, especially if my Ethernet speed was to be around the 900 Mbps range. Even if my Ethernet speed was just a 800 Mbps range...I'd be jumping for joy! Am I really asking for too much here?