Ignite's taper weight and duration are both 1.0, so they won't get much benefit from Necromage, relatively speaking. However, if you have Aspect of Terror buffed by 2/2 Augmented Flames, then it'll be buffed to 21 DPS, up from the base 4 DPS. With Necromage, you'd get 26.25 DPS and it'd last 22.5 seconds instead of 15. Also, if you threw in a custom potion of Fortify Destruction (say 150%, which is easily attainable in the endgame) it should translate to 30 DPS before Necromage, 37.5 with Necromage ... And I'm pretty sure it also benefits from dual casting as well, giving you 66 DPS before Necromage, and 82.5 DPS with Necromage.
I'm not 100% certain about my ordering of buffs here, but I believe I've done the math correctly. Also keep in mind that you can stack an endless number of simultaneous Ignites on any given enemy, so in just a couple seconds, you can apply ~5 of them, taking you to a staggering 400+ DPS. This is all totally irrespective of taper mechanics though.
The taper duration and strength will also be increased, but I don't think it'd make a big difference relatively speaking, since as I said before, they're both set to 1.0 by default (compare to the numbers James gave for Fire Storm above). Also, I believe it'd just add a bit of damage at the end of the 15 (22.5) second span, rather than a separate taper every second. And that magnitude will be based off the DPS, not the cumulative damage. So basically your taper with Ignite will really just manifest as an extra second or two of the spell's DPS at the end of the duration. Nothing game-changing, as most enemies will be dead before the 15 (22.5) seconds are up anyways.
Basically, Ignite can be made extremely powerful, but not via taper exploitation.
Ignite's taper weight and duration are both 1.0, so they won't get much benefit from Necromage, relatively speaking. However, if you have Aspect of Terror buffed by 2/2 Augmented Flames, then it'll be buffed to 21 DPS, up from the base 4 DPS. With Necromage, you'd get 26.25 DPS and it'd last 22.5 seconds instead of 15. Also, if you threw in a custom potion of Fortify Destruction (say 150%, which is easily attainable in the endgame) it should translate to 30 DPS before Necromage, 37.5 with Necromage ... And I'm pretty sure it also benefits from dual casting as well, giving you 66 DPS before Necromage, and 82.5 DPS with Necromage.
I'm not 100% certain about my ordering of buffs here, but I believe I've done the math correctly. Also keep in mind that you can stack an endless number of simultaneous Ignites on any given enemy, so in just a couple seconds, you can apply ~5 of them, taking you to a staggering 400+ DPS. This is all totally irrespective of taper mechanics though.
The taper duration and strength will also be increased, but I don't think it'd make a big difference relatively speaking, since as I said before, they're both set to 1.0 by default (compare to the numbers James gave for Fire Storm above). Also, I believe it'd just add a bit of damage at the end of the 15 (22.5) second span, rather than a separate taper every second. And that magnitude will be based off the DPS, not the cumulative damage. So basically your taper with Ignite will really just manifest as an extra second or two of the spell's DPS at the end of the duration. Nothing game-changing, as most enemies will be dead before the 15 (22.5) seconds are up anyways.
Basically, Ignite can be made extremely powerful, but not via taper exploitation.
