I remember some instances like Ulda allowed 2 groups to go into the same instance. I was wondering if it's possible for us to do that in Heroic instances? Has anyone tried this?

The reason I ask is we're a smallish guild and I'd like to get some of our members working together and getting badges would help too. Better than a PUG and makes Heroics easier if we don't have great gear.

That would require you to make a raid, and raids cant enter an heroic. So no.

I have always thought it would be nice if you could bring 2 groups into regular versions of OL instances for at least one of the reasons you mentioned (small guild). You can do that in all of the old world ones. It sucks when you have 6 or 7 friends/guildies online and everyone wants to run an instance together.

I know it would trivialize some of the content but it was possible at one time.