Yeah, going by gut feel I'd have said that on a ISK/hour basis you'd be better off with a Hulk instead of an Orca unless, as you say, you're running 5 or more Hulks.

For me it's the convenience factor - the Orca has huge tractor range, great capacity and can hold two hulks in the maintenance bay, provides drone support, has a ship fitting facility, and stops can flippers from stealing your ore. Swapping the Orca for a Hulk wouldn't get me any of that. Plus it's a stepping stone on the way to a Rorqual.

As to missions, looks like I've got a lot of rep grinding to do with my team, oh well... at least they'll be well skilled by the time I'm done.