Thank you for the feedbacks, guys.
After investigation, we found out that the issue is mainly caused by pvp matchmaking due to the recent growth in player base. The amount of PvP players is double in the last few months.
There are 3 tiers in pvp: pro, main and beginner. You match the players with the similar elo (you can take it as a hidden win rate) in the same tier most of time. Players will NEVER go down to the lower tier, but can advance to the higher one temporary if the players are performing very well in their own tier.
We reset everyone’s elo to certain value at the start of each pvp and ranked pvp, so losing purposely doesn’t give you advantage. But the current setting is not accurate enough for the amount of the pro tier players nowadays. We will adjust that, and add more different factors to the matchmaking in the coming pvp.
We also notice there are players trying to stay below 100 hero rank in order to stay in the lower tier of pvp. This will be fixed too.
Fun fact: In the current pvp, winners only match winners; losers match losers. So any winning/losing streak means something.