“Time to research”, so to speak, in this game is simply too long. For a single nation for top tier you can spend tens of in-game hours just to research a single top-tier vehicle. And nowadays it’s not rare for a nation to have 4-5-6 rank 8 vehicles, each requiring 400k RP. That’s millions of RP needed for a single rank of vehicles. For air, the situation is even worse, but RP gains there are better as well.
Let’s talk about ground first. Assuming well above average battle (rank7-8, 10 minutes, 2-2.5k mission points, mix of premium vehicles and tech-tree, most time and points spent with premium). For that you’d get around 10k RP. Assuming no time between battles, it’s 60k/hour → a bit less than 7 hours of play for a single vehicle). That’s with premium vehicle, and with premium account. And that is in pretty much ideal “average” condition. You’d have battles getting less RP far more often than battles with more RP.
Without premium time and vehicle the situation is straight up horrible.
In air (at least for me), the situation is a bit easier if using premium plane. Mostly due to the fact that you play the whole game with that plane. You don’t divide your RP between premium and tech tree vehicles, you always get an RP boost. But also, for some reason, time activity in ground gives far too less RP than in air. And in general, same mission point game, with same time spent in game just gives far too less RP in ground.
Let’s compare battles I’ve played recently in both air and ground.
Ground. Whole game played with strv 121 with talisman (714% RP gain).
13 minutes of game, 5k mission points. 28k RP
Air (played with J-7D, 696% RP gain). 10mins of game, around 4-4500 mission points. Let’s say 34k RP (subtracting research bonus)
All the same condition, I did less, played less time and yet got more RP in air. And you are more likely to get battles like that in air, than you are in ground, due to the nature of air battles (at least pre-fox3 spam).
So to sum up: at least as a first step, ground RP gain should be increased to match air (also adjusting for the fact that in ground you play with multiple different vehicles, so naturally your life duration will be kuch shorter there).
And then in general RP gains should be increased for everything. Loads of new vehicles get added, new ranks are created, more and more rp is needed, and yet there are no meaningful increases in research effectiveness.