But if you have an Ignite that is doing 2000 DPS on its own, then having five mages each give up 100 DPS to ensure that it stays on for the entire fight is well worth it. That's kind of the point. Once that ignite slips off, you'll never get it started as well as you did at the start with coordinated use of timers and pyros, etc.

I think whatever I may be losing in base scorch damage is being made up by owning more ignites due to producing more crits. Ideally, I'd test this by taking points out of ignite and then parsing each spell for a few thousand casts, but I can't be bothered wasting the gold. In any case, I haven't seen any kind of dps loss that steep. I'll see if I can get some Theorycraft info.

Edit: Saw Gurg's post above after I posted my own, but he's spot on. The best ignite is always the initial PI-ed, trinketed, Combustioned fireball spam. IMO, keep that one alive, because if it dies it's almost impossible to restack another 5 fireballs quickly and get that rolling again. Our regular tactic is to Combust, slap on some scorches to load up the Imp. Scorch debuff, wait for any ignites to die, and then throw multiple fireballs with a crit-chance bonus thanks to the Combust. After that, it's Scorch until the ignite dies. That particular ignite is going to be comparatively larger to one that's created 'on the fly'. If you've got a 2.5k per tick ignite, then for 5 mages that's like an extra 250dps on top of what they're doing with just scorches. And that ignite is going to go a lot longer than one kept rolling with fireballs.