Having High Latency

I have played this game since Naxx start during Vanilla Classic and I have had a smooth game in terms of latency. On December end a new Christmas event was about to start and i was about to get into the Battle Royale and Pve event, but it started to lag too much where it became unplayable. I qued for the pve event and it was unplayable and so i left and that same lag carried on to the Main game.

I dont know what happened but since then i started lagging. I have factory resetted my computer in case of Virus or some random application(Use anti Virus to clear any Malware as well). I have 300mbps internet speed (when I was having perfect latency I had 150mbps internet, ever since the lag I increased it to see if its that problem but it wasnt) and I even deleted and redownloaded the game itself 3 times(removing cache as well).

This high ping never exsisted before and now all of sudden on the day of that cursed event I starting going through painful lag. I did a lot of trials to figure out this issue and I learnt that at 8pm ST The ping goes back to normal till 4-5am ST. after that the ping goes back to being painful again. Oh! and places like Shatt and Org I cant even enter because the Ping goes to an unusually high amount during my stay there. i have to enter Undercity to be able to use Auction house. I learnt that the ping goes up that much mostly because of the focused population in these main cities(I never had any high lag before the event when i entered these main cities.).

I heard others randomly going through this lag as well but dont know what to do. Please fix.

Oh and to let you know I Play other games like Apex, Valo and Marvels and I have regular ping there (I connect to EU servers to play with a frnd in the UK and I still get good ping). I even played in another realm outside of Warmane and I was having smooth ping. Please help me out here. I hope someone reads this.