Why would you use miasma II single target?

Its dot is 10 potency for 15 seconds, making it both our shortest and by far our weakest DoT.

The total potency for Miasma II is 70, less even than Ruin. Not to mention its prohibitive mana cost, makes it worse than even Ruin II when casting on the move.

So no, miasma II on single target puts you in harm's way (melee) with actually a dps loss.

Might as well take it off your bar, (which I have, ughhhhh its bad), and tridisaster if you actually want adds to die faster. Tri-disaster, btw, is a dps loss over ruin unless there are more than 3 targets. Ruin is 80 pot/2.5 sec, which is 32 pps, while tri-disaster on 3 targets is 90/3 = 30 pps. Furthermore I don't think I have to explain the benefits of focusing down one target first.