I understand how Serina is cheap in 1v1 due to her ice cream truck and cryo+seismic combo, but that same unit isn’t nearly as used in 3v3 (Neither I nor any other Serina player I play with or against has used the unit to freeze bases in a game as a rushing strategy) and the cryo+seismic combo isn’t gameplay changing since there are two other leaders who act as buffers. There are cases where I coordinate with other players to attack in response to said combo, but it doesn’t guarantee we win the encounter. I would also use the hero unit to block off pathways too.
Serina isn’t some unstoppable leader regardless of who you play against and, in fact, when you get double Forge hog rushers, even if you have two or three Serina’s on your team you might as well be any other leader because they can’t compete in speed and damage with Forge.
I read what the update will do and, while values are subject to change, the direction seems to be to decrease radius and damage of the hero unit and combo. Doing that will no doubt solve the Serina problem for you 1v1 players, but not the Forge problem who will still have map control and will also ruin Serina as a useful player in 3v3. Please consider that 343i and CA.