Been playing it. The empire quests change things up slightly.
A lot of them are small bonuses, but a few of them are decent enough to consider going a bit out of your way for. Being the first person to construct a Grand Palace gives you an extra 10 casting points. And the two bonus secret spells from being the first to research a 6th level (or higher) spell (Sage quest) are a bit hit or miss. If your luck is sour, you might get garbage bonus spells, but there are solid odds of getting strong spells out of it. All-Knowing typically comes too late to be relevant, but obviously it has its benefits if you reach that stage. When they say 2 random specializations, that means you can randomly get masteries without their prerequisites.
Wild Magic and Partisan are nice specializations. Partisan does seem to overlap too much with the Rogue class. Some of the stuff stacks well enough with playing a Rogue but you still feel like it's overkill. They have an empire upgrade that gives all lone (ie. stack of 1) units Wetlands, Forest, and Mountain Concealment. Then again you could always get a Sorcerer hero and store up 15 skill points for Master Illusionist at level 7 to get a completely invisible stack (yes, the sorcerer hero provides much better concealment than the rogue hero). The War Anthem morale debuff spell is solid (all enemies take -500 morale if they fail the resist) when it hits and the cheaper mercenary rates naturally makes hiring mercs a better option.
Wild Magic is an interesting contribution. I like Wild Magic Adept as it gives you a bunch of good spells (one is a massive AoE debuff, another gives an enemy +60% all weaknesses, another summons a random lesser elemental which is fairly strong, has a ranged attack, and a unique ability, which can also evolve into a regular elemental, and the last spell switches one unit's position with another random unit of the same tier from another player, very nasty if you use it for hero swaps - can't do leader swaps). That's what a specialization should look like imo, a basket of good options. Mastery has some useful stuff I guess (not too sold on it tbh), and it has two 6th level spells unlike every other mastery which has a 5th and a 7th, so it helps with rushing Sage bonus.
Haven't really tried out halfling race yet. Seems to be the only race with actual evasion (including spell evasion), which can be powerful. Their evasion depends on their morale though. If a Partisan lands a War Anthem on them, halflings are distinctly less impressive. If you ever have halflings on a clover buff though, their evasion gets pretty damn strong. Halfling units seem more unique than the other races, but as I said, I haven't tried them yet. I notice Halfling Apprentices (Sorcerer class unit) get Minor Bard Skills (+200 morale to army) as an extra.
New Seal victory condition creates a decent change of pace from the usual win condition of killing all your enemies.
The new mystic buildings are fairly potent, if you can build them and if you are actually using the shit they upgrade.
I'd say the DLC is decent, all told. You're better off getting it.