Goblins main strength are their archers.
Thing is that their bows lack power and with heavy armour they do little to no damage and rarely penetrate armour.
They are also easy to lure and ambush. They have decent skill in close combat but lack durability.
Their line troops(Skirmishers) are very passive which is easy to exploit. Their weapons lack power and are ineffective against strong armour. But they have decent skills even if they lack HP and armour. Their pikes can be dangerous and nets are really annoying.
Wolf-riders are good only against inexperienced and under equipped troops. Their behaviour rely heavy on flanking and its very easy to exploit. In melee their weapon lack punch. Their mobility make them hard to catch but they are not that great in actual combat.
Shaman is plain and simple big pain in the ass with his wines and swarms of insects.
Overseer is dangerous but he is just one and even with xbow he isn’t that dangerous.
Key is to fight them when you can actually defeat them.
Goblins are bane of low levels and that is why they slaughter militia with easy.
They can be challenging on medium but on high they are pushovers.
If you get 2-3 max leveled 6/0/4 archers you can slaughter them with no losses(especially when you hide behind kite shield wall). Killing 10 goblins on turn make rest broke and run. If not, just shoot them more.
The biggest weakness of Goblin is their passiveness and predictable behaviour.
Sometimes it is just silly. Like 20 Skirmishers getting peppered by archers or enemy attacking you on global map and then sit on their position and letting you retreat with no problems.
The other is lack of scaling. Goblin faction have medium tier units only(with quirks) which make them dangerous to low level enemies but joke against high tier.
Orcs still are the kings of high level fight. Goblins don’t even get close.