This type of complaint nearly always means you're listening to a surround track on a stereo system, without proper "downmixing". This means you're missing the center channel, and instead only hear the front left and front right channels. In surround sound, dialogue mostly goes to the center channel. If you didn't get the video from a good source, the problem could be baked into the video itself.

I have had this problem with multiple commercial streaming sites on two different TVs from two different manufacturers. I’m a little dismayed they haven’t worked this out yet. Not everyone wants to string speakers. “Left” and “right” don’t mean much in some rooms.

In that case you need an AVR that will remix it properly.

Some of the recordings of the first few episodes are known to be bad. It depends on where you watch it (SyFy, Amazon, Netflix, Torrent), and if you watch it with 2 channels or 5/7.

Anecdotically, I've found the Torrented (from SyFy or canadian TV?) and Netflix versions in Stereo to be OK.

Season 1 did have notable audio issues. I found myself having to rewind to understand what was said, and even then it felt like guesswork. I love the show, but do agree with this criticism. Thankfully they straightened it out in later seasons, to the point that I had forgotten about it until I read your comment!

Indeed. I was extremely glad for subtitles for the first few episodes.