Slow down gold, turn on events, fix reward
1) You have increased monster damage at gold mission. It was good. Respawn is much close to players. It's acceptable. But you have increased speed and it's not good. Especially for snipers. Damage+close resp+speed is too much for gold missions. May be you can do a mosters slower. Or more distant resp. Or lower damage. 2 improvements will be enough.
2) There were events like: operation polar star, prophecy, e.t.c. Can you run this events again for new players. It would be desirable to receive this achievements.
3) Some times mission reward is dropping: experience, money, level, but achievements (weapon, finished waves) remain. Can you fix it? Money is important 🙂
3.1) Can you increase a chance of "Black cards"? 1 for 1.000.000 gold for example. Sometimes you can spend 1.5-2m and still nothing.