The rear of the building is brick veneer, with a drainage plane including house wrap and weeps holes as expected. The lower level rear door has gaps around it, particularly just below the steel lintel, where you can see straight in to the house wrap / drainage plane.
Is this considered normal / okay, or should this be sealed. I’m thinking it should be sealed, but wanted to see what others have to say about it.
Yes, the top and the sides of the frame/door casing should be sealed to prevent moisture and insect intrusion.
Yep. What Simon said 
That’s what I was thinking. Thanks.
Sometimes I second guess myself thinking the builder maybe did it for a valid reason I’m unaware of, lol.
That gap is there intentionally for a very good reason, and it should not be filled in with rigid material of any sort. Use a caulk product to seal, not rigid spray foam. As said, wind driven rain protection is essential at that location.
Just tell me why all of you jump through rabbit holes when…
Ok!.. All exterior openings should be property sealed as to prevent moisture and pest intrusion.
Can we all agree with that?
It is just that simple.
You’d better …Yep!
And the house wrap most likely is not UV stable.
Msenty… Right. You mean the drainage plane behind the brick. That’s there for a reason. There are weep holes for that. The gaps and joints around the door should be closed up tho. 
So, provided the brick is properly flashed, then it should be relatively simple to fill that gap, preferably caulking the seam and then filling with a piece of trim. Cap flashing would also be a good idea if you cannot verify and brick flashing.
There are many cases where the BOTTOM edge of something remains open, to allow drainage going down.
Not this case.
Drainage vs. Ventilation Hope that helps.
Am I missing something? I don’t see flashing at the top of the door and lintel. If water gets behind the veneer, it should be able to drain out above the door opening with a properly flashed lintel. It the top of the opening is not correctly flashed, then caulking could create a bigger problem by trapping water trying to drain down the WRB.
Where exactly and what type of flashing do you want to see on a finished veneer wall above a door frame? The flashing is normally behind the first course of brick where the weep holes are above the lintel. It is often hidden once brick is installed. The moisture will exit through the weep holes, it is why they are there. No moisture is supposed to get below properly flashed and installed steel lintel.
Do you have a picture of what flashing you “normally” see in such veneer installation?
NCMA prescribed detail:
