I have the same problem since Chinese New Year. Before that no such problem.

I can randomly get a game that's smooth, but then I have to pray the next game I play doesn't give me 300++ ping. Once I get the high ping, it stays for the game's duration. I can play 10 games in a row, and it's almost a guarantee I'll get 7 laggy games out of the 10.

I'm on Unifi, so not sure if that underwater cable disruption issue has anything to do with it. My friends on Maxis have no such problem. PingPlotter keeps showing me problematic latency on the last 3 routes to the SG server. I notice it clears up at god-forsaken hours starting at 4-5am onwards though, but goes back to shittiness at about 8-9am.

Bloody frustrating. Haven't touched HotS in awhile thanks to this problem.