I haven't actually played a 1v1 Mordor vs Angmar game, but from what I've noticed from my multiple multiplayer matches, I would say that Mordor is currently weak against Angmar.
The early game fight seems pretty even. The spam from both factions can effectively cancel each other out, and they generally start getting heroes around the same time. Angmar might have a slight advantage due to how diverse they can be, but in my opinion, the early game battle is not the problem.
The problem is, if Mordor doesn't get the upper hand during early game, the match seems to be effectively over, with Angmar coming out on top. Once the Men of Carn Dum and Wights start coming out, Mordor doesn't really stand a chance. Wights can turn the tide of games versus any faction if used properly, but against Mordor it is extremely effective becuase of the lack of counters Mordor has to it, as well as Orcs having pretty much no chance against them. The only real counter that have to Wights is Trolls, which aren't too great against Angmar because of the Men of Carn Dumand large Hero roster.
Similarly to the Wight problem Mordor has, Mordor also has a tough time against the Men of Carn Dum, because for how early you can get them, Orcs do basically nothing to them. But the real problem I see is in the Carn Dum Bowmen. Mordor doesn't have even 1 counter to these guys, due to them taking so low damage from trampling, especially once they get their Armor Upgrade. If an Angmar player gets enough upgraded Carn Dum Bowmen, while maintaining enough control of the map, the match is effectively over. And I don't think it's because Carn Dum Bowmen are too strong, besides the trample damage problem, which would help Mordor out a lot.
Anyways, that my opinion. I'd still have to think of ways Mordor can be buffed to counter this, without making them as strong as some previous patches. But making Carn Dum Bowmen take more trample damage will definitely help.