You got some smart ideas, and most of them seem pretty balanced (on their own), but they aren't very connected.
Heroes: The theme is "swarm controllers & bugs", but only the leader has anything fitting that style at all. The rest don't fit it at all.
Examples- The Swarm Caster, apparently has no effect on a Swarm. That makes no sense. What if the Caster had the "swarm is immune to stupid". To balance, the Horror suffers Stupid all the time, but if the leader is within 6", he's immune. So, if you want a swarm-centric band, the caster becomes important. If you want a horde, then the Chittering horde gets play.
Meanwhile, what about the others? Does the Hatchery guard get cheap special armor (same save as heavy armor) made out of giant beetle shells? What does the "arts of Coleopterology" have anything to do with bug catchers? What if they're actually allowed to find bugs? They may search terrain pieces- on a succssful 2D6 of 12, you find a Giant Bug. Place a marker touching the terrain piece that's 2" from the hunter- the bug scurries the 2D6 inches from the marker in a random direction, stopping when he hits the edge of the board or a warrior (which he attacks). On a roll of 2, he joins your band! Or something! Personally, giving 4 guys academic skills when it doesn't fit the fluff doesn't fit, and is too strong.
Equipment: they're animal breeders, without steel whips?
Skills: The cloud of files fits, but the rest don't fit the theme. Maybe the hunters can infiltrate, but no one else? Any bug wrangling / breeding rules? Hive mind rules lets them see what other models see or something?
The Swarm - quite obviously just a troll without changes. Add some bonuses, take a few things away. What if it only had 1 attack, but rerolled all hits once, and ignored -3 armor every time? Maybe he can move through walls (reduces whole move to 1/4 speed, however). Get creative! Also, to steal again from the troll, if you wanted to make a horde undying, it would fit... you're not killing a single bug, you've got plenty more ready to go!
Giant Bug: Interesting. Personally, I would have made them S4, T2, but the way you have it works too. Another option is to reduce the toughness, but give them a huge armor save (for their shell).
Horror: Eh, not that creative as he is now. Can he scale walls? If the small bugs are hurt by fire, is he hurt too?
Personally, I don't see the swarm or the horror as too strong, but I wouldn't let a band take them both at the same TIME. Let them pick one and only one.
What I recommend is that you think, "okay, all bugs have _____ ability." Maybe they're all vulnerable to fire, maybe they all have poison bite (counts as +1 S against living models), they can all climb walls. As a hive mind, they can do _____ . That way, rather than 3 random models with only similar names, you'll get the feeling that a bug behaves like X. If it's a special ability that a skaven can learn / buy, then you have a bridge between the bugs and the rats.