If you pop 300-500 gold attack flags on vampires from the north you will only need 1-2 towers at most assuming you build to the south of the castle. (Watch the number of heroes going to attack early on you will want 4 or more, later on you can level toons off the vampires if you leave them up. Or kill the nearest vampire lair/spawn if the stream is a bit fast with the goblin waves.)
If you place attack flags on the orge lairs when a wave of vampires or goblins come you may be short heroes to handle them without lots of towers. But if you wait until you just finish a round of vampire/goblin wave(s) you have some time to spare to get a couple lairs down and then be free for your next round when you can get a fast response to new flags. Timing of flag placement really helps with various waves.
(Ex- A lair with 100-300 flag may have several heroes on it while a new 500-1k attack flag on a vampire or shaman will have fewer responders until those attacking another flag target, finish destroying the lair or you cancel the flag.)
I like to place 300-500 attack flags on the shaman/vampires, maybe a bit more when I have money to waste, and 100-300 on the stronger individual units.
Make sure you build the SW trade post early on. Some of the other trading post spots are prone to be destroyed but still worth (re)building as needed.
(esp W post underneath vampire castle.)
Sometimes not upgrading posts makes mobs more likely to pass them by; the behavior is not always consistent. (I don't generally tower up the posts for this map, whereas I do in some other maps/missions.)
Fewer towers do make the waves harder but level your heroes more.
Easiest class combo imo, War,Cleric,Rogue,Ranger,Wiz. Add dwarf, paladin and maybe priestess of Agrella and/or second cleric guild.
Party up before or after the dwarves and for paladins later on for NE goblin bases assault.
Just my 3c.
