I've seen posts elsewhere about there being a bug with ignite if you have more than 1 mage. However i can't find a post about it, just people saying they won't be fire until this is fixed. What exactly is the bug?
You seem to be referring to the old vanilla bug where the first mage to proc ignite would get every other mage's ignite counted as his.
As far as i can tell on beta there is next to no munching.
So they fixed the issue where ignite fails to recognize fire spell crits registered when ignite's duration is over 4 seconds? That's the way it is on live, and it is frustrating as hell because you'll land a huge pyro crit and expect a decent ignite for combustion, but it'll wind up being piddly because a living bomb tick crit a millisecond before, refreshed ignite to over 4 seconds, and caused that pyro to not be added to the bank.