Meh, perhaps.

Another approach would be to make something "Scathe Powered".
Again, lets go with the idea that we want to maintain 100 pot/sec while moving, and ~110 while standing.

So lets try this. When you cast Scathe, you get a buff that increases the damage of the next Scathe.
A normal GCD is 2.5s, we want a 2 move combo, so it has to deal a total of 500 potency over 2 moves... Hmm, that ends up being a little too lopsided. So lets drop that down to 450 total and spread it kinda evenly.

Scathe: 150 potency. When you cast Scathe, you get a buff, "Scald", that makes your next Scathe do 2x damage.
So while moving you would always do 2 Scathes, 1 for 150 and the 2nd for 300. And, of course make it so you dont end up consuming the "Scald" buff and immediately reapplying it, resulting in 150 -300 - 300 - 300 - etc.