The current XP progression rate is the disease. Farming is just the symptom

So we have the portal server quota full, just like 2042 in the last weeks.

What is common here?

You have had people do a grind and a lot of people decided that they do not like how long it takes so they have tried to level the classes and weapons faster via portal servers where the bots are generaly easier to take out than players.
These servers can be more or less separated into two categories: The Official rule tag verified experiences that work mostly like normal matchmade servers and those servers which are adjusted specifically for more efficient bot kill farming.

So far what you seem to have done is to make the bot kills give a lot less XP than player kills.

This sounds great on surface but when you think about it, this means that you have made the more normal servers even less efficient and increased the incentive for people to do their darnedest to farm even more efficiently in some servers like those that allow only 1 player inside to farm 62 bots. So there will be even more 1 player servers right now.

What do I propose? I think you need to understand that the farming servers are the "shadow in the cave wall" so to speak. They the silhouettes cast by the glaring issue that is your horrendous XP grind for everything. 
What you need to go is to MASSIVELY reduce the XP needed to unlock everything that is a gameplay unlock instead of a cosmetic/accolades for bragging rights. This will make it so people will either prefer to be more efficient and fight players or that they will be done much faster with their farming servers and there will be less people who want a farming server.

You might want to also bring back the Solo mode from 2042 for the sake of those who just want to grind gun unlocks without players in their way or who just want to PvE.

PS: If all fails please understand that you have a much larger player base than usual and you should be having many more servers for portal or let us rent extra servers