Assuming you are connected through ethernet cable, you are suffering from congestion, talk to your ISP and if they don't fix it then switch to another ISP.
It means they don't have enough bandwidth for all clients. You can see this is a congestion problem because it occurs during the night which is when everybody is at home streaming video and downloading stuff.
It may be a temporary issue, there may be some part of the network that is temporarily down and everything is getting routed through some other place and the capacity of that other place is being exceeded.
They may also have gained many more new clients recently and the equipment that they currently have does not have enough capacity for all those clients and they have to increase the capacity of the network.
You can try something like ExitLag (expensive) or MudFish (relatively cheap). I got better ping (as low as 140 ms) with ExitLag when I was able to find a server that is not blocked by Warmane. I settled for MudFish because it is much cheaper (around 155 ms). You can sign up for a free trial with ExitLag without using a credit card. I'm on AT&T Fiber connecting from North America.
That's not true at all. I've been using paid VPNs on and off for years and I've never been flagged for ban because of them. If you are worried, you can always try one out on an alt account if you have a spare Gmail account.
It could be your ISP doing throttling or traffic shaping if it happens during peak usage times (not yours, overall for their services). Using a VPN might not make any difference.
I really have deep search for this problem but have many questions that would be great if you have good answer for them.
First of all I have same problem with high latency that our dude is specify here specially in pick times of day but I'm just wonder why at this time of the day when I'm going to play Dota 2 or League of Legends I don't experience any shape of lagging or high latency there! If you have logical answer to this question please let us know I spend like 1 month to researching this issue and every time I'm facing dead end.
Maybe a month ago I started on the new Blackrock tbc server. First few days was fine, then for 3 or 4 days every night at peak times I had from 800 to 8000 ms. Literally unplayable. I thought to myself Im going to quit playing here if this issue happens for 1 or 2 more days like this. Luckily out of nowhere the next days were lag free. That continued for 3+ weeks. No problems. Until tonight. Comes same time of the day (evening peak times) and the lag is back and its unplayable. Currently at 6.2k ms.
No lag or delay or anything in any other program or game, or internet browsers. Only on Warmane.
I tried switching to my mobile internet but the problem is still here and i'm still sitting at 6k ms.
Edit: Logging remotely to my work pc and logging in game from there looks like no lag. So is it connected to my home pc specifically?
Edit 2: Lag is now gone just as 2 hours passed since it started. This is exactly same amount of time it took the previous times for the lag to go away. Its literally back to normal 50ms now.