How does crit affect beam spells and DOTs?

Solution 1:

According to some reading on the official forums, there is a mixed consensus on whether DoTs/channels are critting. Some, like you, have noticed the side effects of crits in some DoTs. Some people say they see the bigger yellow crit numbers with channeled spells, and some say they don't.

But the current Blizzard "Known Issues" post says that:

Combat

Damage over time debuffs are not benefiting from items that grant crit chance.

Source

...so clearly DoTs are meant to crit, even if they aren't now. I suspect this applies to channeled spells too.

I do not see this topic mentioned on the current Hotfixes List or in the Patch 1.0.2 info, so I am not sure when it will be further addressed.

Solution 2:

So now with 1.0.3 (maybe got added earlier) DoTs and beamspells crit, you just don't see the delicious yellow numbers but you can tell by them doing more damage than a usual tick would do. Also you can see by other spells profiting from the crits (e.g. Critical Mass passive of the wizard).