open router ports
update modem firmware
This won't do a thing.
Servers are likely overloaded.
On a side note, battle servers were never meant to improve general latency. They were meant to prevent a single bad connection from increasing the latency of everyone. Before, when connections were purely peer-to-peer, every player had to play at the latency of the player with the worst connection, because every player had to wait for the game information from every other player to be sent and received before they could continue.
What the battle servers do is act as a relay. You send your information to the server, the server sends it to everyone else. This means if one player has a particularly terrible connection, the server can still relay the commands of everyone else without having to wait for that one player. That is good for the other players, but it can be very bad for the player lagging, because I'm assuming (haven't been able to play to test) that the lagging player will experience rubber-banding not unlike what happens when you have a bad connection to an FPS server. When everyone has to wait for your bad connection, you never miss any information; it just gets to you a lot slower. If the system stops waiting, the lagging player is going to miss a lot of ticks where his units won't be accepting commands, and therefore won't be moving or will be following the last command that the server received.
As for its effect on latency, it's silly to think battle servers means generally better latency overall. Instead, you're likely to experience more consistent latency, because instead of sending commands directly to your opponents you're sending them to a server, and the location of that server is not likely to change. So if I used to play against my roommate all the time, for example, battle servers are going to introduce more latency for us, because instead of connecting to a machine five feet away from me, I'm connecting to one potentially hundreds of miles away. On the other hand, if I play with someone from Korea all the time, my latency will likely improve, because my point of entry into the network is so much closer.
Battle servers aren't a magical solution to all of CoH2's network problems. It's just a means of normalizing things and giving Relic more control over their own game, instead of relying on Steam.