The stuttering is very noticeable with 45 fps, it's not the way to fix it. I am also experiencing fps drops from 120 to 30-40 when something happens (probably particle system, and lighting). But it still happens the same if I set everything to low (I just gain those 2-3 fps nothing noticeable), this must be the game's fault, it is probably not optimized for having all those 200 players battles in my opinion. I hope I am wrong.
In the beginning of the match when everybody spawns it lags a lot because all 100 players are in the same area. In the end when 3/4 people are dead it lags a lot less.
I thought the game could run with decent fps even with 200 players, since it's the main concept of this dlc to have massive line battles.