Agreed it is quite ridiculous. Being able to destroy any building so easily and pretty much anything else and at the beginning of the game . It needs a massive cost increase or its damage output halved.
The longest fuse giving plenty time to evacuate, the shortest range making it the least likely snare to conect. These 2 things justify its price and damage.
The normal satchal will not kill anything mostly because of the long timer. Hence high damage to denei garrisons. Its primary function.
The range on the at satchel is so short it use is very limited. Thus doing big damage if something finaly gets into range.
If you cant use these two glaring weaknesses to your advantidge its on you.