Hi Caun, sorry I didn't saw your reply at that time.
I don't say I don't struggle with Misty Mountains. I struggle a lot, and I think it's also even more difficult now because your best accessible troop the Gundabad pikemen have a more difficult armorset compared to when the faction was established (pikes are vulnerable at 150 % to swords now), so there is not a lot of things easily accessible you can rely on, but the faction can snowball once Bolg is level 7 and once you reach Dragon's Lair, but that's late in the game. Some AI don't let you go easily at this stage.
The good use of tunnel mechanic I think can buy some time to reach those thresholds, it is a compensation for their cruel lack of strenght in the early game I guess

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Against AI, 2 Gundabad Citadel close to each other with tunnel entrances at opposite side (with mouse control when building the citadel) allowing fast movement of troops backward and forward can be interesting to make a strong defence.
Sometimes, you will want to lose a Gundabad citadel to build Goblin Town without a 4000 resource investment, with the use of Trolls because it can't be auto destroyed unless you get Smaug the Golden

Goblin Town make even better defence against the AI when combined to a Gundabad citadel when the army is good enough (more space defended) and gives economic long term possibilites but it does not give as many fast resources (Gundabad citadel in skirmish gives 40 every 12 seconds which it does not in free build mode where it's 10).
And I play more pve. In pvp, I get easily destroyed
