Yeah, that's pretty low, but that's fairly typical for HD streaming. The audio is 192kbps of that stream (lossy DD 2.0). AVC and VC-1 can do fairly well at low bitrates.
3.2 Mbps streaming data rate is low especially when you consider ST:TNG-R is telecined from 35mm film at 1.485 Gbit/s and mastered to HDCAM SR tape at only 4:1 compression ratio for 10-bit 4:4:4 [color sampling] like the official trailer says at 35 seconds:
Star Trek - The Next Generation Remastered Blu-Ray Official Trailer
The specs on the HDCAM SR format at 4:4:4 10-bit is a 880 Mb/s datarate. So even Blu-ray has a maximum specification Video Bitrate of 40Mbps. Sure there is a difference between 3.2 and 40 when the compression is so high.
A typical blu-ray like The Avengers
is average bitrate of 26 Mbps. So you can do the math of 26 to 880 and
3.2 to 880 to see how much higher the compression ratio is for streaming HD currently
with Internet delivery.