Round table

12 Lizardmen are clearly not enough.

Unless, of course, you're playing as Orrin.
I recently played as him in a Tower map, and 6 stacks of 14 zombies worked great, even though it wasn't even 100 Golems – more like 54, and they only had 8 attacks.

People say that Wistan can clear the hardest Dwarf Strongholds on level 111 in TE.

Well, maybe in TE, because in SoD it's only theoretically possible.
Let's say you have around 25-30 Lizardmen (which is very lucky for SoD).
They'll deal 5-6 damage per hit * 24 = 120-144.
The rest of the meat (Gnolls) should be enough, but in a 20-round battle, it's too risky to rely on the Dwarfs' morale, and that's only if the Stronghold is on a swamp.

P.S. By the way, Dryads are very tactically useful for the Elves, even with their low speed – they're great for defense. You can use them against fast but weak units, like a horde of Pixies. Attack, but make sure they don't break the morale or attack in the 2nd round and damage the Centaurs or, even worse, the Elves – position them so that they can reach the Dryad, and that's it! :
And there's no need to talk about how useful they are for objects like the Preserve or the Gold Mine – they're exactly the kind of slow meat that you can sacrifice in the field, and when defending a castle, they're even more effective, especially against Swamp creatures and all flying units!
And don't forget about their high hit points. At the start, you have 3 * 55 = 165 (not much worse than 2 Wyverns or 2 Griffins), but if you find a lair or save up on the second week and build a +2 growth and upgrade, you'll get 8 * 65 = 520 HP (guaranteed per week) (more than Battle Unicorns and Gold Dragons!).
And lairs are often given out, so with one lair, you get +4 Dryads (260 HP), for a total of 12 * 65 = 780 HP. It's no wonder that on the second week, you should be able to take any Preserve for the Elves (with a minimum number of lairs and only native units – even Shakti has a worse chance of taking the maximum on the second week!).
It's all IMHO