The mini sentry's actually a surprisingly balanced sidegrade, although there are very few people willing to admit it. :thumbup1: Nearly all the classes have a way of dealing with it outside its range, and its hitbox is actually taller than the actual mini itself [the same as a level 1 sentry].
It might be balanced on that part, but its heavily broken on an other.
Normaly an engineer takes time building a nest. It gives slow progress but gives a good holding point. Objective wise: if you manage to get your nest at the objective, you should be rewarded with a good chance of taking it. The problem lies on being able to get that sentry up there.
With the mini sentry it no longer matters if they shoot it down. They are forced to take out that sentry as soon as its built. And even though it does only half the damage of a normal level 1. That still is alot considering the engineer only has to reveal itself for less than a second. Its dumping the sentry and retreating. Once its down repeating the process. Its low cost allows you to even do that multiple times.
The mini sentry isnt bad balance wise. Its simply an anoying weapon to face. There is no fun at all when you are fighting 2 engineers using that tactic. You need someone dedicated to take them out to even get a chance to counter them.
With normal sentries they often are put back since its very hard to get them that close to an objective. It makes it less fun for the engineer but gives an area that allows normal pvp combat. Combat that people find fun.
People dont care that sentry guns lock down areas like the last cp on dustbowl. They simply want a fun battle which mini sentries cant give.
Not only that, but the frontier justice which in design on its own is fine. It becomes broken with a mini sentry. You just dump the weapon and its very likely to gain assits which is free crits.
Balance isnt the only thing required to design a good weapon. Avoiding frustration is also important. If people get frustrated alot they just leave the game. And on a longer timespan its bad to have that.
What happens in a pub when a good player faces a team with mainly mini sentries and his team cant battle them? He swaps teams. He doesnt even care about trying since its boring and frustrating. And this only amplifies the problem.
Its why the gunslinger is called broken. Its not a fun weapon except for its user. And guess what also has that same 'feature': Exploits. Exploits are only fun for their users and not for those facing them. Exploits give no risk at all other than getting kicked/banned from a server. And to face an exploiter isnt fun.
Nerfing might reduce its problem, but it doesnt fix it. Even when they remove its knockback entirely its still a spam weapon that doesnt require skill other than knowing where to place it to make it anoying.