It's a combination of a number of factors. The hull, shield modifier, base turn rate, console setup (5 tac and 4 eng), two universal LT boffs (factoring in some of the BoP flexibility, with NONE of the disadvantages of the BoP stats), and .22 impulse mod (making it the fastest ship in the game). It has the best escort tanking ability (aside from possibly the MVAM and Fleet Patrol Escort), AND it has enough potential firepower to shred through Tactical Team buffs (unless there's a big buff like EPtS 2 or 3, something certain escort/raider setups can't factor in well without sacrificing DPS).
It's possible to kill it 1v1, but you have to have a build specifically intended to kill bugships, and you have to be GOOD. Most of the time, it takes a small team of opponents to kill it. . .for something that's supposed to be an 'escort'. Not even a particularly 'heavy' one, either.
The effectiveness of the bugship also depends on the pilot. An unskilled pilot won't be able to make quite as much use of the bugship as a top-notch elite one. Even in the hands of a lesser-skilled pilot, it's a very effective escort, just prone to being a little more killable.
It's the best or tied for the best escort in every stat except for sci consoles, add in defense bonuses from AP:O and Evasive maneuver and you get an escort that can out tank the average Fed cruiser while putting out bleeding edge damage.
Any COH player can testify to the value of not getting hit as a perfectly valid tanking stratagem.
It's available to both factions so on at least that scale it's "balanced" but against every other ship in the game it wins. Only the fleet defiant can match the damage out put but that ship is no where near as tough or flexible by design. That's part of the reason I get tired of people complaining about how powerful the fleet defiant is, it's got one worthless boff and any BOP or Bug will out fly it pretty handily if they want to.
It's not really "OP", but it does have a very nice set of stats.
Escorts are differentiated between themselves by having certain advantages over each other: be it a more useful (non-Tac) Ensign slot, 5 Tac consoles instead of 4, a better turn rate, some neat tricks opened up by a non-Tac LC slot, maybe some Universal slots, more Hull, better Shields, more Turn rate,...
The Jem'Hadar Attack Ship has most of those:
- Non-Tac Ensign? Check.
- 5 Tac Consoles? Check.
- High Hull? Well, it's not the highest (anymore), but out of the 8 Fleet Escorts+bugship, it ranks 4th (Qin-F>Akira-F>Somraw-F>JHAS>Prometheus-F=Hermes-F>Defiant-F>Saber-F>lolAquarius-F), ~4% above average.
- Good Shields? Highest base Shields for Escorts, if by a tiny margin (1 mod vs .99 for a few others).
- Universal slots? Check. Though tbh, they don't make much of a difference in this case.
- High Turn Rate? Check. In fact, it's closer to BoP territory than Escort territory!
And on top of that, it has a better Impulse mod, meaning it reaches fights sooner... an advantage not to underestimate.
It technically makes it easier to cap Defense as well, but tbh that's easy on any Ship.
The only downside is that it has 4 Eng Consoles for only 1 Sci, so in practice it has weaker Shields than most Escorts (less Field Gens), despite the higher base mod.
Overall, it has the advantage over all other Escorts. Not a huge, insurmontable advantage, but an edge nonetheless.
Ok its not op in a sense but the fact that it can out turn a defiant and when used by a skilled pilot it is a pain to kill. I have a patrol escort and i have faced bug captians i cant kill them unless they have been weakened already. Why?? You ask because they out turn me and destroy my shields before i can return fire. The turn rate for a bug is to me a annoyance, 20 is insane and if u add an ability like EPtE u dont have a prayer. good ship but outclasses all of the current top tier escorts.