Those calculations are good. I’m more on the playstyle of the build he is trying to accomplish. He has burst damage and waiting for that additional damage on a 10 sec time isn’t really a good choice. If the mobs are not yet dead, MM can be used.
The only time I see Ignition well worth it is if you have a lot of +buff on magic attack like Blessing and Swell Left Arm, and on grinding party, this is already frowned upon when group of mobs are dead within sec.
Now with the upcoming nerf posted by Ellyr, ignition is a further waste of hits.
I can see Ignition very viable on solo play fighting with Elites and by no means Ignition can’t be used as another set of equipment. If you feel using that, go ahead.