Imagine how much different the episode would’ve been if Ember and Thorax had been casually saying things that fed Spike’s fear the whole time, rather than undermining it. For instance, Ember saying “at least you ponies aren’t [doing exactly whatever Thorax was doing in the last cutaway]” or Thorax talking about how much better than Chrysalis he is, except his descriptions are ambiguously close to describing Ember.  
That would’ve also made it a bit more of a surprise (although no less predictable) when the two of them got together and found each other immediately relatable.

I would have figured they wouldn’t get along like anyone else, but this lakeside chat really worked.
 
It’s like if Fluttershy and Rainbow Dash met later in life.