Warlock – “Clan Leader” [Campaign 4, Mission 1]

I'm playing through all the Campaigns on Hero difficulty, and I'm really struggling to progress in this particular mission. There's very little money and resources, and while there's a gold mine near my castle, it's guarded by High Vampires, against whom I have no chance, considering my hero's level and the troops I have. And to even reach those Vampires, I have to kill a lot of Dancing Skeletons, which is impossible to do without taking losses, given their high initiative, which further reduces my chances in the battle against the Vampires. Other important mines are also guarded by numerous troops of levels 2-3. So, how am I supposed to develop, considering I only have one month? Of course, I could just sit tight, build what I can, buy what I can, wait, and then eventually defeat the last opponent, but I'd really like to upgrade my hero, visit the arena, and build a guild. The arena is guarded by many upgraded Lizard Riders. So, how am I supposed to kill them with 50 Assassins and 10 Furies? I have even fewer chances against them than against 40 High Vampires. I don't really want to lower the difficulty, as I've completed all the other Campaigns on Hero difficulty so far (although I did curse a lot during the Agrael campaign, but I still managed to finish it). I'm currently trying to figure out how to get a foothold on this map: how to quickly deploy Furies (and not lose them), who have high initiative and attack without retaliation, and clear out the slow neutral creatures (Golems, Zombies). But I have no idea what to do about the Vampires, the Dancing Skeletons, and the Elven Archers. I guess the only option is to wait until the end of the month, build up my strength, and try to defeat them without significant losses. Has anyone actually completed this map on Hero difficulty?