Ember gun is a very good epic weapon. Not sure it's overpowered however. Combined with nomad it's very effective. 

dear friend you are still without experience and the further you go, the more inexplicable things will become to you. example?? like you, after you have sweated, or spent, and raised the power of your weapons, inexplicably you find yourself less and less powerful. .. One of many. pay attention to the game. and don't spend unnecessarily, here the clever are rewarded... and the BOTs. spending to play against an AI is not worth it.. the weapon you indicated will seem less and less powerful.. the further you go the more difficult it will be

I dont know the exact level you are at currently, but the "players" that are using Ember Gun arent real players, but bots/AI to fill up matches. Real players dont really have strong or good Ember Guns because the weapon isnt very long in the game (or atleast not at the point you are at right now). Bots/AI (i will just refer to them as bots) do  use Ember Gun where you are at right now alot. The reason Ember Gun bots (or bots with any Close Quarter weapon) are so strong is because bots always have unrealisticly good implants and pilots. At the level you are at right now real players only have Rare implants and a few Epic implants and maybe 1 Legendary implant if they got very lucky, they also mostly use Epic pilots and maybe Neymar JR with every now and the a legendary pilot. Bots on the other hand have alot of Legendary and Epic Implants, and almost always use Legendary pilots way more often. Bots with Close Quarter weapons always have the best and longest range and high DMG because of that. It actually doesnt matter which level you are on (except the highest level), bots basically always have a stronger hangar than you. When you get to Tier 5 on Gear Hub i advice getting Aegis and Disc Launcher 8, having Guardian is also good but does not work against Ember Gun.