A change to the Ranking System that SHOULD happen.
When you are in your promos to the next tier/division. You can lose LP in those Promos, and be set back based on how you did in the promos. What I mean by this is that if you go 0-2 in your promos you'll be lower LP than you were if you went 1-2 (depending if the game you won is your 2nd).
Now, this shows that depending on how you do in promos will depend on how set back you get to get back into them. However, why does it not work the other way around too?
What I suggest is that you should be able to exceed 100LP while in your promos, or if it's the win to put you in your promos. The amount of LP you have that is over 100LP divided by 2 is the amount you'll start with in your next rank, if you rank up. This will reward players doing well in their promos, and it'll fix the problem where you are at 95LP and win to only get 5LP when you normally get 25LP (this is just an example).
Let's go over some examples to help you understand the idea, if how I explained it is not meshing for you.
Scenario 1: You are at 75LP. You gain 25LP each win, and lose 20LP each loss. You win your game and to your promos at exactly 100LP. You then go 2-1 in your promos. This will mean: (25 - 20 + 25 = 30 / 2). You'll start with 15LP in the next Division you get into.
Scenario 2: You are 90LP. You gain 20LP each win, and lose 20LP each loss. You win and get to your promos with 110LP. You then go 2-0 in your promos. This will mean: (10 + 20 + 20 = 50 / 2). You'll start with 25LP in the next Division you get into.
This idea still needs to be refined, but you should be rewarded for doing better than you have to do in your promos.