I have a full rear bumper and like it for the utility, but it really doesn't improve the departure angle much. The factory bumper skin is tight against the rear crossmember (at the hitch). What a rear bumper does improve is the side skirt clearance behind the rear wheels a lot, and when you drag, you have the reassurance you aren't destroying the side skirts.However, like you mentioned, a swing-out carrier that utilizes the OEM bumper skin offers no benefit in rear departure angle.
I do wish it made more of a difference on true departure angle, but the LX 'H' mode does help with that quite bit, luckily.