But, in battles this category doesn’t works.
I have in the same team a blue 4* heroe: Grim, with an “average” mana speed and they almost activate their special movements at the same time.
Why?
How many blue tiles makes the diference between an average and fast mana speed category?
1 tile?
Do you have Alasie in your team?
Do you feel her mana speed is “Fast”?
Without mana troop or mana node in talent, average need 10 puzzles while fast need 8.
Grimm with mana node and level 17 mana troops only need 9 puzzles. It can also be achieved without mana node in talent if the mana troop is at level 23:
Mana node in talent + level 17 mana troop:
9 × (100%+2%+11%) = 10.17 > 10
9 is enough to charge.
No mana node in talent but with level 23 mana troop:
9 × (100%+0%+13%) = 10.17 > 10
9 is enough to charge.
Alasie without mana node in talent and without level 29 mana troop will still need 8 puzzles:
No mana node in talent and with level 28 or lower mana troop:
7 × (100% + 0% + 13%) = 7.91 < 8
7 is not enough, still need 8.
By matching 3 blue puzzles 3 time, you had use 9 blue puzzles, which means bot of them are fully charged.
Are you sure you did not ghost some blue tiles (sending them through an empty space)? In that case it counts as 2 tiles.
Here is a chart made by @flyingsolow which shows exactly how many tiles every hero needs and what you can do to reduce the number of tiles required. Remember, ghosting counts as two tiles. So if you send 2 tiles into an empty space without hitting a hero, it will count as 4 tiles.
Maybe this will help more than numbers. Take a look. This is a screen shot from your vid, around 0:20, where you can see the difference between fast and average charging after 6 blue tiles. It’s quite noticeble. Tap the screenshot for a better view.
At 0:51 you make another 3 tiles blue combo, charging Alasie (a total of 9 tiles) but leaving Grimm uncharged. Only two seconds after, at 0:53, during the cascade blows a red dragon that activates the blue tile next to it, bringing the blue tiles total up to 10, and charging Grimm. 100% normal.