I found a thread ealier about this but did not see a resolution and now can't seem to find it.

I have a speed tuned team for nightmare clan boss consisting of:

Helicath ; Vizier; Frozen Banshee (turn meter skill turned off); Warcaster; and Skullcrusher  - This runs through to the end and has decent damage, but I wanted to experiment

I substituted Venus in for her defense down and HP burn for Frozen Banshee. Without changing any speed stats, the turn order has changed. Skullcrusher goes sooner and Helicath is a bit slower it seems. 

None of the Champs have turn meter reduction nor increase speed that I can see, yet the entire system is FUBAR just by changing out a champ. The same thing happens when I put in Fahrakin (i turn off the ally attack). Perhaps I'm missing something. Please tell me if I am!

Why do the speeds/turn order change with these champs even though gear/turn meter/speed stats haven't?

I run on PC and iPad.

I appreciate your time, thank you