Let's look at the forces involved:
The Valloreans are organized into thirty-five Legions, each having 10,000 Legionnaires. The Vallorean army will no doubt have plenty of supplies, engineers, extra equipment, and formidable magical support from enchanted war machines, powerful warrior-clerics, and dreaded wizards. The Valloreans can also expect to have various contingents of elves, dwarves, halflings, as well as other races and beings, including some ogres and small units of Cloud-Giants.
So the damnable Valloreans boast 35 legions of 10,000 men. (And all those legions are at full strength? Are these quasi-Roman legions or Xerxes-esque "immortals"?)
The legions are primarily heavy infantry with plenty of siege engineers. Their auxiliaries include elves, dwarves, halflings, etc., and small numbers of Ogres and Cloud Giants. More importantly, they have powerful Clerics and Wizards. (In a later post, we learn that they have flying cavalry too -- not in great numbers though, I assume.)
On our side we have:
(1) Commander: 50th level.
(12) Elite Specialists: 30th level.
(24) Lords: 20th level.
(1) Wang-Liang/Half-Fiend General. (30th level)
(2) Wang-Liang/Half-Fiend Lords. (20th level)
(30) Wang-Liang/Half-Fiends (16th level)
(300) Wang-Liangs (12th level)
(38) Fire-Giants (20th level.)
(24) Cloud-Giants (20th level.)
(15) Chimera's
(12) Manticore's
(600) Vampires (6th-12th level)
(880) Werewolves (4th-12th level)
(2800) Ogres (under 10th level)
(26,000) Hobgoblins (standard levels as organized).
(100,000) Humans (minimum of 2nd level, majority Fighters).
So, against their 350,000 elite human heavy infantry and auxiliaries, we're supposed to pit our ~150,000 humans, hobgoblins, and assorted monsters. Let's look at our strengths and weaknesses.
Our Wang-Liang are effectively Trolls that can turn invisible or disguise themselves. That is, they're big, strong, and immune to most attacks (except fire and acid). I'd love to be able to send Wang-Liang skirmishers against mundane heavy infantry. They can do some damage, withdraw -- with some dead foes for "rations" -- come back fresh, and so on. They can also ambush quite effectively, using their invisibility. Perhaps they can even disguise themselves and infiltrate a camp that doesn't have much magical support. We can't risk Fireballs and Flame Strikes though. Disguised as mundane Ogres, the Wang-Liang might not draw so much fire.
The Vampires have many stengths and at least a few obvious weaknesses. Vampires and their spawn are, of course, vulnerable to sunlight and to Clerical magic, but they have an amazing capacity for spawning more of their kind -- particularly in the short term, since they "spawn" quickly and won't run out of "food" in the time frame of this military campaign. The two nearby cities might find their "noncombatants" (women and old men) quickly conscripted into the Midnight Legions. Also, Vampires don't have to advertise their nature. Armed as soldiers, adult, male Vampires should blend in fine (during a night attack).
The Werewolves, as lycanthropes, don't "spawn" as quickly and effectively as the Vampires. Perhaps they can use their curse behind enemy lines or in guerrilla skirmishes -- the high-level Clerics can't be everywhere -- but they don't end up with powerful slaves. In the vast forests, they should make good scouts and quasi-cavalry, and they may have enough wolves there to command as auxiliaries.