@heme725 Actually that low fire rate didn't balance at all.
As you mentioned, Damage really matters when firing the first round. And Mastiff can land 100+ damage if you can really aim, and 2 shots can take out a purple shield character (or red shield if you are lucky to land headshots). This only takes 0.625 second to do this (without bolt). But with R99, since it has a low damage of shots, so we can just use DPS to calculate, which is 198. That means we need ~1 second to kill a purple shield guy. If you are too bad that cannot land 2 shots of 100+damage on the opponent, then you are doomed. But if you do, then your opponent will be melted.
The problem is that things become worse if you are already injured, mastiff will likely kills you in one shot, so unless you also bring a gun with high-damage per shot (ignoring DPS), you cannot win a fight like this.