After the ban, we decided to test this on someone's personal server running on Anathema code. We gave each of the mages 100% critical strike, and he was able to get ignite to tick for 50k+ without Power Infusion. Testing with Power Infusion greatly accelerated the accumulation of ignite damage (it was ticking for 250k+). Ignite has been known to be an extremely difficult ability to code and Blizzard themselves changed it to where mages each get his/her own ignite. So the bug most likely lies within ignite and not Power Infusion or other modifiers like AP.
The chances for this bug to occur greatly increases with critical strike chance from world buffs and a higher number of mages.
See:
http://wowwiki.wikia.com/wiki/Ignite_(old)#Known_bugs